Resistor Colour Code Calculator

Work out resistor colour code instantly with clear inputs, formula shown and shareable results.

About Resistor Colour Code Calculator

A four-band resistor encodes two significant digits, a power-of-ten multiplier and a tolerance. Brown-black-red-gold is 1, 0, times 100, so 1 kΩ at 5%. The tolerance band matters as much as the value: a 5% 1 kΩ part is guaranteed only to lie between 950 and 1050 ohms.

Formula

Colour code

R = (digit1 x 10 + digit2) x 10^multiplier, with the tolerance band giving the guaranteed spread

Worked example

With the default values below, Resistor Colour Code Calculator returns Resistance of 1,000.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

First bandone of Black (0), Brown (1), Red (2), Orange (3), Yellow (4), Green (5), Blue (6), Violet (7), Grey (8), White (9): Brown (1)
Second bandone of Black (0), Brown (1), Red (2), Orange (3), Yellow (4), Green (5), Blue (6), Violet (7), Grey (8), White (9): Black (0)
Multiplier bandone of Black (x1), Brown (x10), Red (x100), Orange (x1k), Yellow (x10k), Green (x100k), Blue (x1M), Gold (x0.1), Silver (x0.01): Red (x100)
Tolerance bandone of Brown (1%), Red (2%), Gold (5%), Silver (10%): Gold (5%)

Results

Resistance: 1,000.00 Ω
Value: 1 kΩ ±5%
Minimum within tolerance: 950.00 Ω
Maximum within tolerance: 1,050.00 Ω

Step by step

1Values used
2Colour code
3Resistance= 1,000.00 Ω
4Value= 1 kΩ ±5%
5Minimum within tolerance= 950.00 Ω
6Maximum within tolerance= 1,050.00 Ω

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Electrical results are planning estimates only. Verify against the applicable wiring rules (IEC 60364, BS 7671, NEC or local code) and have all installation work designed and checked by a qualified electrician.

Frequently Asked Questions

Which end do I read from?

Start at the band nearest an end and furthest from the tolerance band. Gold and silver are almost always tolerance, so read away from them.

What about five-band resistors?

Precision parts use three significant digits plus multiplier and tolerance, so brown-black-black-brown-brown is 100 x 10 = 1 kΩ at 1%.