Resistor Calculator

Decode a resistor's 4-band, 5-band, or 6-band color code into its resistance in ohms and tolerance percentage.

Free to use · Instant results

Calculator Inputs

Number of Bands

Choose how many color bands your resistor has.

Band 1

First significant digit (all band counts).

Band 2

Second significant digit (all band counts).

Band 3

4-band: multiplier. 5-band/6-band: third significant digit.

Band 4

4-band: tolerance. 5-band/6-band: multiplier.

Band 5

5-band/6-band only: tolerance. Ignored in 4-band mode.

Band 6

6-band only: temperature coefficient. Ignored in 4-band/5-band mode, and never used in the resistance or tolerance calculation.

Resistance: 1 kΩ
Resistance (Ω): 1,000.00
Tolerance: 5%

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How It's Calculated

Formula

\text{4-band: } R = (10 d_1 + d_2) \times m \\ \text{5/6-band: } R = (100 d_1 + 10 d_2 + d_3) \times m

Resistors are marked with colored bands instead of printed numbers because the bands stay readable regardless of the resistor's orientation. Each color stands for a digit (0-9), a power-of-ten multiplier, or a tolerance percentage, following the standard EIA/IEC resistor color code used industry-wide. A 4-band resistor encodes two significant digits, a multiplier, and a tolerance. A 5-band or 6-band resistor encodes three significant digits, a multiplier, and a tolerance for tighter precision; a 6-band resistor adds a sixth band for temperature coefficient (how much resistance drifts per degree Celsius), which this calculator accepts for completeness but does not use, since resistance and tolerance are the only two values this tool reports. Gold and silver never appear as significant digits — they are reserved for the multiplier band (×0.1 and ×0.01) and the tolerance band (±5% and ±10%).

Worked Examples

4-band: Brown-Black-Red-Gold

Digits: Brown=1, Black=0 -> significant = 10
Multiplier: Red = x100
Resistance = 10 x 100 = 1000 Ω = 1 kΩ
Tolerance: Gold = ±5%

5-band: Brown-Black-Black-Red-Brown

Digits: Brown=1, Black=0, Black=0 -> significant = 100
Multiplier: Red = x100
Resistance = 100 x 100 = 10000 Ω = 10 kΩ
Tolerance: Brown = ±1%

Frequently Asked Questions

Why can't gold or silver be a significant digit?

Gold and silver are reserved exclusively for the multiplier band (x0.1 and x0.01, for resistors under 10 ohms) and the tolerance band (±5% and ±10%). The standard resistor color code never assigns them a digit value, so this calculator rejects them if entered in a digit position.

What does the 6th band do on a 6-band resistor?

The 6th band on a real 6-band resistor indicates its temperature coefficient (how many parts per million its resistance drifts per degree Celsius). This calculator accepts that band for completeness, but since it only reports resistance and tolerance, the 6th band's value does not affect the calculated result.

Why do I choose 4-band, 5-band, or 6-band first?

The band count determines which bands are digits versus the multiplier and tolerance: a 4-band resistor uses 2 digits, while 5-band and 6-band resistors use 3 digits for tighter precision. Selecting the band count tells the calculator how to interpret the colors you choose.