ElectroHub

Resistor Colour Code Calculator

Colour bands encode a resistor's value because printing digits on a 2 mm cylinder is impractical. Decode bands to a value, or work the other way and find which bands to look for.

Resistor Color Code

Pick the band colors. Leave band 3 as "none" for a 4-band resistor.

Resistance
Tolerance
Type
  1. 1.Digit bands: red → 2, red → 2, orange → 3 → significant figures 223
  2. 2.Multiplier band: brown → ×10
  3. 3.FormulaR = significant figures × multiplierSubstituteR = 223 × 10ResultR = 2.23 kΩ
  4. 4.Tolerance band: gold → ±5%

The formula

Value = (digit bands) × 10^multiplier, ± tolerance band

Bands 1–2
significant digits (plus a third on 5- and 6-band parts)
Multiplier
power of ten to apply
Tolerance
gold ±5 %, silver ±10 %, brown ±1 %, red ±2 %

Worked example

Brown, black, red, gold.

  1. Brown = 1, black = 0 → digits give 10
  2. Red multiplier = ×10² = ×100
  3. 10 × 100 = 1000 Ω

1 kΩ ±5 % — so anything from 950 Ω to 1050 Ω is in spec.

Where you'll use it

Reading parts out of the drawer, and the reason a measured 980 Ω resistor is not faulty. The tolerance band sits slightly apart from the others, which tells you which end to read from.

The laws behind it

Parts this applies to

Resistor (fixed)Potentiometer / Rheostat / TrimmerResistor Array / NetworkThermistor (NTC / PTC)Varistor / MOVSupercapacitorLED (light-emitting diode)MOSFET

Related calculators

SMD Resistor Code Calculator3/4-digit: value = (leading digits) × 10^(last digit)Capacitor Code CalculatorValue in pF = (first two digits) × 10^(third digit)Series and Parallel Resistance CalculatorSeries: R = R₁ + R₂ + …Ohm's Law CalculatorV = I × R