Antibiotic Stock Calculator Guide: Stock Concentration, C₁V₁ = C₂V₂, Working Solutions, and Unit Conversion
Laboratory antibiotic stocks are concentrated solutions that can be diluted into growth medium or another validated laboratory preparation to reach a protocol-specified working concentration.
The existing Antibiotic Stock Calculator performs two linked calculations. First, it calculates stock concentration from the mass of antibiotic powder and the stock-solution volume. Second, it uses the standard dilution relationship C₁V₁ = C₂V₂ to determine how much of that stock is required for the desired final working solution.
For example, dissolving 500 mg of antibiotic to a final stock volume of 10 mL produces a concentration of 50 mg/mL. If the desired working concentration is then 100 µg/mL in 100 mL total medium, the concentration units must first be made compatible before the dilution equation is applied.
The central dilution principle is conservation of solute amount during an ideal dilution: the amount of antibiotic contained in the aliquot of concentrated stock equals the amount of antibiotic present in the final diluted preparation. This gives C₁V₁ = C₂V₂.
Thermo Fisher uses the same C₁V₁ = C₂V₂ relationship for preparing working stocks and serial dilutions in laboratory applications.
Unit consistency is particularly important because antibiotic stocks are often stated in mg/mL while working concentrations are stated in µg/mL. One milligram equals 1,000 micrograms, so a stock of 100 mg/mL is equivalent to 100,000 µg/mL.
Addgene, for example, lists commonly used bacterial-selection stocks such as ampicillin at 100 mg/mL with a 100 µg/mL working concentration, kanamycin at 50 mg/mL with 50 µg/mL working concentration, and chloramphenicol at 25 mg/mL with 25 µg/mL working concentration. These examples correspond to 1,000-fold stock-to-working concentration ratios.
Those values are protocol examples, not universal biological recommendations. The appropriate antibiotic, concentration, solvent, storage conditions, and application depend on the plasmid, organism, cell system, antibiotic formulation, and laboratory protocol.
The calculator should therefore perform arithmetic rather than prescribe an antibiotic concentration. Users should obtain the required working concentration and preparation conditions from the relevant plasmid documentation, product datasheet, institutional SOP, or validated experimental protocol.
The same principle applies to solvent choice. Some laboratory antibiotics are commonly dissolved in water, while others may require ethanol, DMSO, or another specified solvent. Addgene explicitly lists solvent differences for several commonly used antibiotics.
Sterility and stability are also outside the dilution equation. C₁V₁ = C₂V₂ can produce a mathematically correct volume while the physical preparation is unsuitable because of degradation, incompatible solvent, contamination, precipitation, temperature exposure, or an incorrect biological concentration.
The calculator is therefore best used as a transparent laboratory arithmetic tool after the experimental protocol has already established what solution should be prepared.
How to Calculate Antibiotic Stock and Working-Solution Volumes
- Confirm the protocol-defined antibiotic concentration: Obtain the intended working concentration, solvent, preparation conditions, and storage requirements from an appropriate laboratory protocol or product source before using the calculator.
- Enter antibiotic powder mass: Enter the mass actually used to prepare the concentrated stock.
- Enter final stock-solution volume: Use the final prepared stock volume rather than merely the initial solvent volume if those values differ.
- Review calculated stock concentration: The calculator divides antibiotic mass by stock volume and reports the resulting mass-per-volume concentration.
- Enter desired working concentration: Use the concentration specified by the established experimental protocol.
- Enter desired final working volume: V₂ means total final prepared volume.
- Match concentration units: Convert mg/mL, µg/mL, or other supported concentration units before applying C₁V₁ = C₂V₂.
- Generate the working recipe: The calculator returns stock volume V₁ and the remaining diluent volume needed to reach the selected final volume.
- Check whether the volume is practically measurable: Extremely small stock volumes can be difficult to dispense accurately and may require an approved intermediate dilution strategy.
Formula and variables
The first equation calculates mass-per-volume stock concentration from antibiotic mass and final stock-solution volume. The second equation conserves antibiotic amount during dilution. All concentration units must be compatible before solving, and V₂ represents the intended final solution volume rather than simply the starting diluent volume.
Stock concentration: C₁ = m / V_stock; Dilution: C₁V₁ = C₂V₂; therefore V₁ = (C₂V₂)/C₁; Diluent volume ≈ V₂ − V₁- m — Antibiotic mass
- Mass of antibiotic used to prepare the stock solution, such as mg.
- V_stock — Stock-solution volume
- Final volume of the prepared stock solution.
- C₁ — Stock concentration
- Concentration of the prepared antibiotic stock.
- V₁ — Stock volume to add
- Volume of concentrated stock required in the final working preparation.
- C₂ — Desired working concentration
- Protocol-specified target antibiotic concentration in the final preparation.
- V₂ — Final working volume
- Total final volume after stock and diluent are combined.
Scenario 1: Ampicillin Stock Added to 500 mL Medium
An established bacterial-selection protocol calls for 100 µg/mL ampicillin in 500 mL final medium, and the laboratory has a 100 mg/mL stock.
- Stock concentration C₁
- 100 mg/mL
- Desired working concentration C₂
- 100 µg/mL
- Final volume V₂
- 500 mL
- Convert the stock concentration to compatible units.
- 100 mg/mL = 100,000 µg/mL.
- Use V₁ = C₂V₂/C₁.
- V₁ = (100 µg/mL × 500 mL) / 100,000 µg/mL.
- V₁ = 0.5 mL.
- 0.5 mL = 500 µL.
- If treating V₂ as an exact final volume, corresponding diluent volume is approximately 500 − 0.5 = 499.5 mL.
Result: Stock required = 0.5 mL = 500 µL.
The 100 mg/mL stock is 1,000 times the 100 µg/mL working concentration. Addgene provides the same stock and working concentrations as a standard bacterial-selection example.
Understanding your results
Calculated stock concentration
This is the mass of antibiotic per unit volume in the concentrated stock prepared from the entered powder and stock volume.
The result does not verify antibiotic potency, purity, or formulation.
Stock volume to add
This is V₁ from the dilution equation.
It represents the quantity of stock needed to supply the required antibiotic amount to the final preparation.
Diluent volume
When volume additivity is assumed, diluent can be calculated as final volume minus stock volume.
For protocols requiring an exact volumetric final volume, preparation should follow the specified laboratory method rather than assuming every liquid combination is exactly additive.
Dilution factor
The ratio C₁/C₂ describes how concentrated the stock is relative to the working solution when compatible units are used.
A 100 mg/mL stock used at 100 µg/mL is a 1,000-fold concentration ratio.
Practical pipetting check
A mathematically valid V₁ can still be inconvenient or inaccurate to pipette if it is extremely small.
That is a preparation issue rather than an error in C₁V₁ = C₂V₂.
Assumptions
- The intended antibiotic and working concentration have already been established by an appropriate laboratory protocol.
- The stock is sufficiently dissolved and homogeneous for concentration-by-volume calculations.
- Antibiotic mass and stock volume represent the prepared stock being used.
- C₁ and C₂ represent compatible mass-per-volume concentration definitions.
- V₂ represents the final total working-solution volume.
- The antibiotic amount is conserved during dilution.
- No degradation, precipitation, chemical reaction, or loss is modeled.
- Volume additivity is assumed where diluent volume is calculated as V₂ − V₁.
- The calculation is intended for laboratory solution preparation rather than clinical, veterinary, or patient dosing.
Limitations
- The calculator performs concentration and dilution arithmetic only.
- It does not determine which antibiotic should be used for a plasmid, organism, cell line, or experimental system.
- It does not determine the biologically appropriate working concentration.
- Addgene explicitly recommends checking the plasmid datasheet or plasmid map for the relevant resistance marker and antibiotic.
- The calculator does not determine solvent compatibility. Some antibiotics use water while others may require ethanol, DMSO, or another specified solvent.
- It does not determine stock sterilization requirements.
- It does not determine storage temperature, light sensitivity, freeze-thaw limits, shelf life, or stability.
- It does not account for antibiotic degradation after stock preparation or after addition to culture medium.
- It does not correct for active ingredient potency, salt form, hydration state, supplier assay percentage, or molecular-weight differences between antibiotic forms.
- A mass concentration such as mg/mL cannot automatically be converted to molarity without molecular weight and formulation information.
- The simple concentration calculation assumes the entered mass corresponds to the relevant antibiotic material being expressed in the selected mass units.
- The dilution equation does not itself guarantee biological efficacy.
- Very small calculated volumes can exceed practical pipetting accuracy.
- The calculator does not replace institutional biosafety procedures, laboratory SOPs, or manufacturer instructions.
- It must not be used as a medication, patient, or veterinary dosing calculator.
Common mistakes
- Entering mg/mL and µg/mL as though the numbers were directly comparable.
- Forgetting that 1 mg = 1,000 µg.
- Using starting diluent volume as V₂ instead of final solution volume.
- Using powder mass directly in C₁V₁ = C₂V₂ without first calculating stock concentration.
- Using an antibiotic concentration copied from another organism or protocol without confirming applicability.
- Assuming every antibiotic should be prepared as a 1,000× stock.
- Assuming every antibiotic uses water as the solvent.
- Ignoring the antibiotic formulation or salt form.
- Adding the stock volume on top of an already complete final volume when an exact final volume is required.
- Confusing µL with mL.
- Using a stock concentration different from the actual prepared concentration.
- Treating a tiny calculated volume as automatically practical to pipette.
Practical use cases
Scenario 2: Calculate stock concentration
500 mg of laboratory reagent is prepared to a final stock volume of 10 mL.
Stock concentration = 500/10 = 50 mg/mL.
Scenario 3: 1,000× bacterial-selection stock
A validated protocol uses a stock concentration 1,000 times the working concentration.
For a 100 mL final preparation, the stock volume is one-thousandth of the final volume when the concentration ratio is exactly 1,000.
Scenario 4: Kanamycin example
Addgene lists 50 mg/mL stock and 50 µg/mL working concentration as a common bacterial-selection example.
Those concentrations differ by a factor of 1,000.
Scenario 5: Small calculated aliquot
The equation returns 0.7 µL stock for a small working preparation.
The arithmetic may be correct, but the laboratory should use an approved preparation strategy if that volume cannot be dispensed accurately.
Scenario 6: Verify an existing protocol
A protocol already specifies stock concentration, working concentration, and final medium volume.
Use the calculator to independently verify the required stock addition.
Planning and decision guide
The calculator has two sequential concentration problems
First determine what stock was prepared.
Then determine how much of that stock belongs in the working preparation.
Stock concentration is mass divided by volume
For mass-per-volume stocks, C = m/V.
The units follow the selected mass and volume units.
Scenario 7: 250 mg in 5 mL
C = 250 mg / 5 mL.
Stock concentration = 50 mg/mL.
The denominator must be final stock volume
Concentration describes the amount per final solution volume.
If a protocol says dissolve and bring to a specified final volume, use that final volume.
Mass-per-volume concentration is not mass fraction
50 mg/mL means 50 milligrams of material per milliliter of solution.
It should not be interpreted as 50% by mass.
Mass concentration is also different from molarity
Molarity expresses amount of substance in moles per liter.
Converting mg/mL to mol/L requires molecular weight and the correct chemical form.
Scenario 8: Why molecular form matters
Two salts of an antibiotic can have different molecular weights.
The same mg/mL therefore need not represent the same molar concentration.
C₁V₁ = C₂V₂ follows conservation of solute amount
The aliquot taken from the stock contains C₁V₁ antibiotic amount under compatible units.
After dilution, that same amount is represented by C₂V₂.
Thermo Fisher uses the same relationship for laboratory dilution calculations
Its application material explicitly calculates source volume from C₁V₁ = C₂V₂.
The same arithmetic applies to the stock-to-working dilution here.
Solve stock volume directly
V₁ = C₂V₂/C₁.
The concentration units cancel when C₁ and C₂ are expressed compatibly.
Scenario 9: 50 mg/mL to 50 µg/mL
50 mg/mL = 50,000 µg/mL.
For 100 mL final volume, V₁ = 50 × 100 / 50,000 = 0.1 mL = 100 µL.
The same result can be recognized as a 1:1,000 dilution
50,000 µg/mL divided by 50 µg/mL equals 1,000.
One part stock is therefore present in 1,000 parts final solution.
A 1,000× stock refers to concentration ratio
C₁/C₂ = 1,000.
It does not mean adding 1,000 volumes of stock.
Scenario 10: 1,000× stock into 100 mL final volume
V₁ = 100 mL / 1,000.
V₁ = 0.1 mL = 100 µL.
Addgene commonly uses 1,000× antibiotic stocks
Its bacterial culture and agar protocols describe 1,000× stock preparation and 1:1,000 use for several common selection antibiotics.
Do not generalize 1,000× to every antibiotic or biological application
The ratio is convenient for common bacterial-selection examples.
The required concentration must still come from the relevant experiment and protocol.
Ampicillin is a common calculation example
Addgene lists 100 mg/mL stock and 100 µg/mL working concentration.
Those values form an exact 1,000-fold concentration ratio.
Carbenicillin can use a similar stock arithmetic example
Addgene lists 100 mg/mL stock and 100 µg/mL working concentration in its general bacterial-selection reference.
Biological behavior and stability still differ from ampicillin.
Chloramphenicol demonstrates solvent differences
Addgene lists a 25 mg/mL stock and notes ethanol as the solvent in its bacterial-selection table.
This illustrates why dilution arithmetic cannot choose the solvent.
Coumermycin demonstrates another solvent-specific example
Addgene lists DMSO for its stock preparation example.
Again, solvent information must come from the protocol rather than C₁V₁ = C₂V₂.
The current calculator correctly separates arithmetic from preparation guidance
Its existing page states that solvent compatibility, sterility, storage, stability, and biological requirements must come from approved protocols or product documentation.
That boundary should remain prominent.
Unit conversion is one of the main failure points
1 mg = 1,000 µg.
Therefore 1 mg/mL = 1,000 µg/mL.
Scenario 11: 25 mg/mL
25 mg/mL = 25,000 µg/mL.
Do not compare the number 25 directly with a target stated in µg/mL.
Volume conversion is equally important
1 mL = 1,000 µL.
A result of 0.2 mL is therefore 200 µL.
Scenario 12: Convert stock volume
V₁ = 0.075 mL.
Equivalent volume = 75 µL.
A user-friendly result should show both mL and µL when appropriate
Small stock additions are often physically pipetted in microliters.
Displaying both units reduces mental conversion errors.
The final volume convention must be clear
In C₁V₁ = C₂V₂, V₂ is the final total volume.
If V₂ is 100 mL and V₁ is 0.1 mL, an exact-volume preparation conceptually contains stock within that total 100 mL.
Adding stock to 100 mL already-prepared medium changes the exact final volume
100 mL medium plus 0.1 mL stock gives approximately 100.1 mL total, not exactly 100.0 mL.
In many routine biological protocols this tiny difference may be operationally accepted, but mathematically it differs from an exact final-volume preparation.
The interface should state which convention it uses
The current recipe calculates diluent as V₂ − V₁, which corresponds to treating V₂ as the intended final volume.
That is the cleanest mathematical interpretation.
Scenario 13: Exact 100 mL final preparation
V₁ = 0.1 mL stock.
Idealized remaining diluent = 99.9 mL to reach 100 mL total.
Volume additivity is still an approximation
Real liquid mixing can show slight nonadditivity.
For routine dilute laboratory preparations this may be negligible, but high-precision analytical work can require volumetric preparation methods.
The calculator should not turn concentration into a protocol recommendation
Its job is to calculate the consequence of the entered target.
It should never say that a particular working concentration is biologically correct merely because it appears in a common-reference table.
Different organisms can require different selection conditions
Antibiotic susceptibility and resistance expression vary among organisms and systems.
A bacterial plasmid-selection concentration should not automatically be transferred to mammalian cell culture or another organism.
The plasmid resistance marker must match the antibiotic
Addgene advises checking plasmid documentation for the appropriate resistance marker and antibiotic.
Dilution arithmetic cannot detect a resistance-marker mismatch.
Scenario 14: Correct arithmetic, wrong antibiotic
The calculator perfectly prepares an ampicillin concentration.
If the plasmid carries a different resistance marker, the biological selection setup is still wrong.
Stock concentration should reflect the actual prepared solution
If the powder amount or final stock volume differs from the nominal recipe, use the actual values.
Do not assume a nominal stock concentration that was not prepared.
Scenario 15: Underfilled stock
A nominal plan was 500 mg in 10 mL, but final volume was actually 8 mL.
The concentration would be 62.5 mg/mL, not 50 mg/mL.
Powder purity or potency can matter in specialized preparations
A supplier may report potency, assay percentage, hydration, or salt form.
The basic mass-per-volume calculator does not correct for those factors.
Do not silently add a potency correction
That requires product-specific information and changes the meaning of the entered mass.
A future advanced mode could support explicit potency correction if scientifically justified.
Molar antibiotic stocks require a different input architecture
To prepare mol/L concentrations from powder, molecular weight is required.
This calculator is currently structured around mass-per-volume antibiotic stocks.
Use a molar-solution calculator when molarity is the target
The existing site already links a Molar Solution and Media Preparation Calculator from this page.
That keeps the search intent appropriately separated.
Very small V₁ values deserve a warning
The current page already notes that a very small calculated volume can be difficult to pipette accurately.
That should become a quantitative UI guardrail where pipette capabilities are known.
Scenario 16: 0.2 µL stock volume
The mathematical calculation can be valid.
A routine laboratory pipette may not deliver that volume accurately, so an approved intermediate dilution may be necessary.
Do not invent a universal minimum pipetting volume
Pipette ranges and accuracy specifications differ by instrument.
The appropriate threshold should come from the equipment specifications.
Intermediate dilution adds another C₁V₁ = C₂V₂ stage
A concentrated primary stock can first be diluted to an intermediate stock.
The intermediate can then be used to prepare the final working solution.
A future intermediate-stock mode would be useful
It could solve two sequential dilution stages while maintaining exact unit tracking.
The current page should not automatically recommend one unless the user intentionally selects it.
Serial dilution is related but not identical
Serial dilution repeatedly applies a fixed dilution step.
The current antibiotic workflow generally calculates one stock-to-working dilution.
The generic dilution calculator should retain the broad intent
The site already links a dedicated Dilution Calculator from the antibiotic page.
Antibiotic Stock should remain laboratory-antibiotic specific.
Stock stability is antibiotic-specific
Addgene recommends frozen aliquots for several common bacterial-selection stock workflows and discusses antibiotic-specific preparation.
The calculator should not transform this into one universal storage rule.
Repeated freeze-thaw behavior is outside the arithmetic model
Even a correctly calculated concentration can change in practical usefulness through degradation or handling.
Protocol instructions govern those issues.
Temperature during media preparation can matter
The current page warns against adding heat-sensitive antibiotics before media have cooled as required by the protocol.
That is an appropriate preparation warning but should remain protocol-dependent.
The calculator should not prescribe an exact addition temperature
Different antibiotics and protocols have different stability constraints.
Use the validated preparation procedure.
Sterility is not produced by arithmetic
A concentration calculation says nothing about whether the stock or final preparation is sterile.
Aseptic technique and protocol-specific sterilization methods remain separate laboratory requirements.
The calculation can be verified through amount balance
After solving V₁, calculate C₁V₁ and C₂V₂ independently.
They should match after unit normalization.
Scenario 17: Balance check
C₁ = 100,000 µg/mL and V₁ = 0.5 mL gives 50,000 µg.
C₂ = 100 µg/mL and V₂ = 500 mL also gives 50,000 µg.
This is an excellent implementation invariant
The calculator can internally confirm the amount balance after every calculation.
A mismatch indicates a unit-conversion or arithmetic bug.
The stock-concentration calculation can also be cross-checked
C_stock × V_stock should reproduce the entered antibiotic mass under compatible units.
This provides a second internal validation layer.
Scenario 18: Stock check
50 mg/mL × 10 mL = 500 mg.
The product reproduces the original powder mass.
Round only after the calculations are complete
Unit conversion and dilution arithmetic should use full internal precision.
The final displayed pipetting volume can then be formatted to an appropriate resolution.
Avoid false pipetting precision
A result such as 137.284619 µL may exceed the meaningful precision of the preparation and equipment.
The UI can retain the computational value while displaying a practical rounded amount.
The calculator should show the concentration ratio
C₁/C₂ immediately tells the user whether the stock is 10×, 100×, 1,000×, or another concentration factor.
This is a useful sanity check.
Scenario 19: Unexpected dilution factor
A user expected a 1,000× stock but the calculated C₁/C₂ is only 100.
That signals that either the stock preparation or entered target differs from the expected protocol.
The result should distinguish calculated values from protocol values
Calculated: stock concentration and required V₁.
User/protocol supplied: antibiotic identity, target working concentration, solvent, storage, and biological application.
This distinction improves scientific trust
The calculator can be highly authoritative about arithmetic without pretending to decide experimental biology.
That is especially important for laboratory YMYL-adjacent content.
The page should explicitly exclude medical dosing
The current site already states that the tool is not intended for clinical or veterinary dosing.
That boundary should remain in both limitations and FAQ content.
The strongest result is a transparent recipe
Calculated stock concentration.
Stock volume required.
Diluent volume.
Dilution factor.
Unit conversions used.
Recommended calculation audit trail
500 mg / 10 mL = 50 mg/mL.
50 mg/mL = 50,000 µg/mL.
V₁ = C₂V₂/C₁.
Diluent = V₂ − V₁.
The next calculation step belongs to the experimental protocol
Once the arithmetic is known, the protocol determines how and when that solution should actually be prepared and used.
The calculator should stop at that boundary.
Frequently asked questions
What does an antibiotic stock calculator do?
It calculates a stock concentration from antibiotic mass and solution volume and then determines the stock volume required for a specified working concentration and final volume.
What formula does this calculator use?
It calculates stock concentration with C₁ = mass/stock volume, then uses C₁V₁ = C₂V₂ to solve the working dilution.
What does C1 mean?
C₁ is the concentration of the antibiotic stock solution.
What does V1 mean?
V₁ is the volume of stock solution required.
What does C2 mean?
C₂ is the desired final working concentration specified by the laboratory protocol.
What does V2 mean?
V₂ is the intended final total working-solution volume.
How do I calculate antibiotic stock concentration?
For a mass-per-volume stock, divide antibiotic mass by the final stock-solution volume.
What is 500 mg in 10 mL?
500 mg / 10 mL = 50 mg/mL.
How do I calculate the volume of antibiotic stock to add?
Use V₁ = C₂V₂/C₁ after making the concentration units compatible.
Does C1V1 = C2V2 convert units automatically?
The mathematical equation requires compatible units. The calculator should normalize supported units before solving.
How many micrograms are in one milligram?
1 mg = 1,000 µg.
How many microliters are in one milliliter?
1 mL = 1,000 µL.
What does a 1,000x antibiotic stock mean?
Its concentration is 1,000 times the intended working concentration.
How much of a 1,000x stock goes into 100 mL final solution?
Mathematically, one-thousandth of the final volume: 0.1 mL or 100 µL.
Is ampicillin commonly prepared as a 100 mg/mL stock?
Addgene lists 100 mg/mL stock and 100 µg/mL working concentration as a common bacterial-selection example.
What is a common kanamycin stock concentration?
Addgene lists 50 mg/mL stock and 50 µg/mL working concentration as one common bacterial-selection example. Use the concentration specified for your own protocol.
What is a common chloramphenicol stock concentration?
Addgene lists 25 mg/mL stock and 25 µg/mL working concentration for one common bacterial-selection workflow and specifies ethanol in that example.
Are those antibiotic concentrations universal?
No. They are protocol examples. The appropriate antibiotic and concentration depend on the organism, resistance marker, experimental system, and validated procedure.
How do I know which antibiotic to use with a plasmid?
Check the plasmid datasheet, plasmid map, or other validated documentation for the resistance marker. Addgene specifically recommends this check.
Does every antibiotic dissolve in water?
No. Solvent requirements are antibiotic-specific. Addgene lists ethanol or DMSO for some antibiotic stock examples.
Can this calculator choose the solvent?
No. Use the product documentation or validated laboratory protocol.
Does the calculator tell me how to sterilize the stock?
No. Sterility procedures are protocol-specific and outside the dilution calculation.
Does the calculator tell me how to store antibiotic stocks?
No. Follow the applicable supplier or laboratory protocol for storage, aliquoting, light protection, and stability.
What if the calculated stock volume is too small to pipette accurately?
The arithmetic can still be correct, but an approved intermediate dilution or another preparation strategy may be required based on the available equipment.
Should I add stock to the full final volume or subtract its volume first?
Mathematically, C₁V₁ = C₂V₂ treats V₂ as final total volume. If exact volume matters, the preparation should be brought to the specified final volume according to the laboratory protocol.
Can I convert mg/mL to molarity with this calculator?
Not without molecular weight and the correct chemical form. Use a molar-solution calculator for that task.
Does antibiotic salt form matter?
It can matter for molecular-weight, potency, and formulation calculations. The basic mass-per-volume calculator does not automatically correct for salt form.
Can I use this for cell-culture antibiotics?
The arithmetic can apply when an established cell-culture protocol already specifies the stock and target concentration, but the calculator does not determine biologically appropriate culture concentrations.
Can this calculator be used for patient medication dosing?
No. It is intended for laboratory solution preparation, not clinical or veterinary dosing.
What is the difference between this and a dilution calculator?
A generic dilution calculator begins with an already known C₁. This calculator can first calculate C₁ from antibiotic powder mass and stock volume and then perform the working dilution.
What is the difference between this and a molar solution calculator?
This calculator works primarily with antibiotic mass-per-volume stocks. A molar-solution calculator uses molecular amount and molecular weight to prepare molarity-based solutions.
How can I verify the result?
After unit conversion, check that C₁V₁ equals C₂V₂. Both sides should represent the same antibiotic amount.
How accurate is an antibiotic stock calculator?
The arithmetic and unit conversion can be highly accurate from valid inputs. Actual preparation accuracy depends on weighing, volumetric measurement, pipetting, product potency, solution stability, and adherence to the laboratory protocol.
Sources and review
- Pouring LB Agar Plates — Antibiotic Stock and Working Concentrations — Addgene. Accessed 2026-09-02.
- How to Inoculate a Bacterial Culture — Preparing Antibiotics — Addgene. Accessed 2026-09-02.
- Molecular Biology Reference — Antibiotic Concentrations — Addgene. Accessed 2026-09-02.
- Creating Standard Curves With Genomic DNA or Plasmid DNA — C₁V₁ = C₂V₂ — Thermo Fisher Scientific. Accessed 2026-09-02.
- Diluting TaqMan Primers and Probes — Dilution Calculations — Thermo Fisher Scientific. Accessed 2026-09-02.
Reviewed 2026-09-02 by Dr Akawak Ejigu, DBA.