Resistor Calculator
Decode resistor colour bands to find the resistance value, or calculate the total resistance of resistors in series or parallel.
Select the colour of each band from left to right (the tolerance band is at the right end and is wider-spaced).
Resistance value
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Tolerance: —
Range: —
Enter resistor values (in ohms). Add as many as you need.
Series total
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Parallel total
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Resistor Color Code Chart
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1,000 | — |
| Yellow | 4 | ×10,000 | — |
| Green | 5 | ×100,000 | ±0.5% |
| Blue | 6 | ×1,000,000 | ±0.25% |
| Violet | 7 | ×10,000,000 | ±0.1% |
| Gray | 8 | ×100,000,000 | ±0.05% |
| White | 9 | ×1,000,000,000 | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
| None | — | — | ±20% |
How to Read a 4-Band Resistor
- Band 1 — first significant digit
- Band 2 — second significant digit
- Band 3 — multiplier (×10^n)
- Band 4 — tolerance (gold = ±5%, silver = ±10%)
How to Read a 5-Band Resistor
Precision resistors add a third significant digit:
- Bands 1–3 — three significant digits
- Band 4 — multiplier
- Band 5 — tolerance (brown = ±1%, red = ±2%)
Series and Parallel Resistance
Series
$$R_{total} = R_1 + R_2 + R_3 + \ldots$$
Resistors in series simply add. Total resistance is always greater than any individual resistor.
Parallel
$$\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + \ldots$$
For two resistors in parallel: $R = \frac{R_1 \times R_2}{R_1 + R_2}$
Total parallel resistance is always less than the smallest resistor.
Frequently Asked Questions
What does resistor tolerance mean? Tolerance indicates how close the actual resistance is to the marked value. A 1,000 Ω resistor with ±5% tolerance could measure anywhere from 950 Ω to 1,050 Ω. For most circuits, ±5% (gold band) is fine; precision analog circuits may require ±1% (brown band).
How do I tell which end to read the colour bands from? The tolerance band (gold, silver, or a precision colour) is always at the right end and is separated by a larger gap. Start reading from the left (the end closest to the first band with no gap).
What is the E12 / E24 resistor series? Resistors are manufactured in standard value series — E12 (12 values per decade) and E24 (24 values per decade) are the most common. When designing a circuit, choose the nearest standard value. The E24 series provides values like 10, 11, 12, 13, 15, 16, 18, 20, 22, 24, 27, 30, 33, 36, 39, 43, 47, 51, 56, 62, 68, 75, 82, 91 ohms per decade.
