Pressure converter guide
Pressure is force divided by area. The pascal (Pa) is the SI derived unit equal to one newton per square metre, and this converter uses pascals as its common base.
Atmosphere labels are not interchangeable: the standard atmosphere is exactly 101,325 Pa, while the technical atmosphere is 98,066.5 Pa. A torr is defined as one 760th of a standard atmosphere and is labeled separately rather than being silently treated as any mercury-column unit.
How to convert pressure units
- Enter pressure: Provide a finite number in the selected source unit.
- Choose the source: Select the exact pressure unit and atmospheric convention.
- Choose the target: Select the output unit or use Swap to reverse the pair.
- Convert: Select Convert pressure to calculate through pascals.
Formula and variables
Each input is first expressed in pascals and then scaled to the target unit.
target pressure = source pressure × (pascals per source unit) ÷ (pascals per target unit)- pₛ — Source pressure
- The signed finite pressure value entered.
- fₛ — Source factor
- Pascals represented by one source unit.
- fₜ — Target factor
- Pascals represented by one target unit.
Convert standard atmosphere to kilopascals
Express one standard atmosphere in kPa.
- Amount
- 1
- From
- atm
- To
- kPa
- 1 atm = 101,325 Pa
- 101,325 Pa ÷ 1000 Pa/kPa
Result: 1 atm = 101.325 kPa.
The standard-atmosphere definition makes this conversion exact.
Understanding your results
Absolute and gauge values
A unit conversion preserves the number’s pressure reference. It does not convert gauge pressure to absolute pressure or the reverse.
Negative values
Negative gauge or differential pressure can be meaningful. Negative absolute pressure is not physically interpreted by this calculator.
Assumptions
- One standard atmosphere is exactly 101,325 Pa.
- One torr is exactly 1/760 of a standard atmosphere.
- One bar is exactly 100,000 Pa.
- The input pressure reference—absolute, gauge, or differential—does not change during unit conversion.
Limitations
- The converter does not change between absolute and gauge pressure.
- It does not compensate for altitude, weather, temperature, or fluid density.
- Mercury-column units are excluded because their conventions require careful specification.
- Displayed precision should not exceed the source measurement precision.
Common mistakes
- Mixing gauge pressure with absolute pressure.
- Treating standard and technical atmospheres as equal.
- Assuming torr and every mmHg convention are identical.
- Confusing psi with ksi.
- Using a rounded factor too early in a multi-step calculation.
Practical use cases
Mechanical and process work
Compare specifications reported in psi, ksi, bar, kPa, or MPa on a consistent pressure basis.
Laboratory and atmospheric work
Translate standard atmospheres and torr while retaining the pressure reference and unit convention.
Planning and decision guide
Record the pressure reference
Write abs, gauge, or differential with the converted value when relevant. Unit conversion alone cannot recover a missing atmospheric reference.
Frequently asked questions
How many kilopascals are in one atmosphere?
One standard atmosphere is exactly 101.325 kPa.
How many pascals are in one psi?
One pound-force per square inch is approximately 6894.757293168361 Pa.
Is one bar the same as one atmosphere?
No. One bar is exactly 100 kPa, while one standard atmosphere is exactly 101.325 kPa.
Is torr exactly the same as mmHg?
A torr is exactly 1/760 atm. Mercury-column unit values depend on their stated convention, so this converter does not relabel torr as mmHg.
Does converting psi gauge produce psi absolute?
No. The converter changes units only; it does not add or subtract atmospheric pressure.
Sources and review
- NIST Guide to the SI, Appendix B.9: Factors for Units Listed by Kind of Quantity or Field of Science — National Institute of Standards and Technology. Accessed 2026-08-29.
- NIST Guide to the SI, Chapter 4: The Two Classes of SI Units and the SI Prefixes — National Institute of Standards and Technology. Accessed 2026-08-29.
Reviewed 2026-08-29.