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Resistor Calculator

Decode 3–6 band resistor color codes, combine resistors in series or parallel, and calculate round-wire conductor resistance.

Resistor Color Code

ExampleSample values — edit any field to see your result.

Results update as you type.

Resistance

52 MΩ ±5%

Estimated result

Resistance in ohms
52,000,000.00000000000000Ω
Tolerance
±5%

Band interpretation

BandColorMeaning
1greenfirst digit
2redsecond digit
3bluemultiplier
4gold±5%
Resistance52 MΩ ±5%
Decode three-, four-, five-, or six-band resistor colors, combine any list of resistors in series or parallel, or calculate the resistance of a round conductor.

Formula

Color code: R = significant digits × 10^multiplier.

Series: Rtotal = ΣR. Parallel: Rtotal = 1 / Σ(1/R).

Round conductor: R = length / (conductivity × π × (diameter/2)²).

Examples

Green, red, blue, gold

Green and red form 52, blue multiplies by 10⁶, and gold is ±5%, giving 52 MΩ ±5%.

Copper conductor

A 100 m copper conductor, 0.05 cm in diameter, at 59,600,000 S/m has 8.5452318438602 Ω resistance.
For parallel entries, every branch must have a positive resistance. A zero-ohm branch represents a short circuit and needs separate treatment.

Frequently asked questions

How do resistor color bands work?
The first bands are significant digits, followed by a power-of-ten multiplier, tolerance, and on six-band resistors a temperature coefficient.
How do resistors add in series?
Series resistances add directly, R total = R1 + R2 + more.
How do resistors combine in parallel?
The reciprocal total is the sum of reciprocals, 1/R total = 1/R1 + 1/R2 + more.
What controls a wire's resistance?
Resistance grows with length and falls with conductivity and cross-sectional area.

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