Calculate resistor values based on color bands
Resistor Calculator
Calculated Resistance:
How Resistor Color Codes Work
Resistors are electronic components that limit the flow of electric current in a circuit. Most resistors use a color code system to indicate their resistance value and tolerance. The 4-band resistor color code is the most common type.
Reading a 4-Band Resistor:
- 1st Band: First significant digit of the resistance value
- 2nd Band: Second significant digit of the resistance value
- 3rd Band: Multiplier (the power of 10 to multiply the first two digits by)
- 4th Band: Tolerance (the accuracy of the resistor value)
Example Calculation:
For a resistor with Red (2), Red (2), Red (×100), and Red (±2%):
- First digit: 2
- Second digit: 2
- Multiplier: ×100
- Value: 22 × 100 = 2,200 ohms or 2.2 kΩ
- Tolerance: ±2% means the actual value could be between 2.156 kΩ and 2.244 kΩ
Color Code Reference Table:
| Color | 1st Band | 2nd Band | 3rd Band (Multiplier) | 4th Band (Tolerance) |
|---|---|---|---|---|
| Black | 0 | 0 | ×1 | – |
| Brown | 1 | 1 | ×10 | ±1% |
| Red | 2 | 2 | ×100 | ±2% |
| Orange | 3 | 3 | ×1,000 | – |
| Yellow | 4 | 4 | ×10,000 | – |
| Green | 5 | 5 | ×100,000 | ±0.5% |
| Blue | 6 | 6 | ×1,000,000 | ±0.25% |
| Violet | 7 | 7 | ×10,000,000 | ±0.1% |
| Gray | 8 | 8 | ×100,000,000 | ±0.05% |
| White | 9 | 9 | ×1,000,000,000 | – |
| Gold | – | – | ×0.1 | ±5% |
| Silver | – | – | ×0.01 | ±10% |
Common Standard Resistor Values:
Resistors are manufactured in standard values based on their tolerance series. Some common values include:
- 10 Ω
- 22 Ω
- 47 Ω
- 100 Ω
- 220 Ω
- 470 Ω
- 1 kΩ
- 2.2 kΩ
- 4.7 kΩ
- 10 kΩ
- 22 kΩ
- 47 kΩ
- 100 kΩ
- 220 kΩ
- 470 kΩ
Pro Tips:
- Always read the resistor from the side with the band closest to the end.
- Resistors have no polarity, so they can be installed in either direction in a circuit.
- The 4th band (tolerance) is typically spaced slightly further from the other three bands.
- Some newer resistors use 5 or 6 bands for more precise values and temperature coefficients.
4-Band Resistor Color Code
Resistors are electronic components that limit or regulate the flow of electrical current in a circuit. A common way to specify a resistor’s value is by using color bands. In a 4-band resistor, these colored rings indicate the resistor’s value (in ohms), along with the tolerance, describing how accurate that value is expected to be.
Color Code Basics
The 4-band code is read from one end of the resistor to the other. Usually, the first band is the one closest to a lead (the metallic wire extending from the resistor’s body) or is visually separated from the rest. The four color bands have the following meaning:
- 1st Band: First digit of the resistor value
- 2nd Band: Second digit of the resistor value
- 3rd Band: Multiplier (the power of 10 factor)
- 4th Band: Tolerance (e.g., ±5%, ±10%, etc.)
Each color corresponds to a specific digit or multiplier. The digits 0–9 are assigned standardized colors (e.g., black = 0, brown = 1, red = 2, and so on). Tolerances are indicated by certain colors like gold (±5%), silver (±10%), or no band (±20%).
Color Code Table
Below is a general reference for the color-to-digit and color-to-multiplier assignments. Note that some manufacturers might have slight variations, but these are the most commonly accepted standards.
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | × 100 | N/A |
| Brown | 1 | × 101 | ±1% |
| Red | 2 | × 102 | ±2% |
| Orange | 3 | × 103 | N/A |
| Yellow | 4 | × 104 | N/A |
| Green | 5 | × 105 | ±0.5% |
| Blue | 6 | × 106 | ±0.25% |
| Violet (Purple) | 7 | × 107 | ±0.1% |
| Gray | 8 | × 108 | ±0.05% |
| White | 9 | × 109 | N/A |
| Gold | – | × 10-1 | ±5% |
| Silver | – | × 10-2 | ±10% |
| No Band | – | – | ±20% |
Formula for Resistor Value
The value of a 4-band resistor in ohms (Ω) can be expressed as:
- D1: Digit represented by the first band
- D2: Digit represented by the second band
- M: Multiplier represented by the third band
The fourth band indicates the tolerance. For example, a gold band typically means ±5% tolerance.
Example: Brown, Black, Red, Gold
Let’s decode a resistor with the color bands: Brown (1st) – Black (2nd) – Red (3rd) – Gold (4th).
- D1 (Brown) = 1
- D2 (Black) = 0
- M (Red) = 102 = 100
- Tolerance (Gold) = ±5%
Using the formula:
So the resistor value is 1 kΩ (1000 ohms) with a tolerance of ±5%.
Example: Red, Violet, Orange, Silver
Suppose the color bands are Red (1st) – Violet (2nd) – Orange (3rd) – Silver (4th).
- D1 (Red) = 2
- D2 (Violet) = 7
- M (Orange) = 103 = 1,000
- Tolerance (Silver) = ±10%
Using the formula:
So the resistor value is 27 kΩ (27,000 ohms) with a tolerance of ±10%.
- 4-band resistors show two digits, a multiplier, and a tolerance.
- The first two color bands give the numeric digits, and the third band sets the multiplier.
- The fourth band indicates tolerance—often ±5% for gold, ±10% for silver, and so on.
- If unsure which side is the first band, look for the side with a band closer to the resistor’s end, or the group of three consecutive bands that are spaced closer together.
Mastering the 4-band resistor color code helps in quickly identifying resistor values without needing additional equipment. Once you recognize the standard color-to-digit mappings and the multiplier roles, reading resistor values becomes second nature in electronics work.
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