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Full changelogEngine 1.18.3

Resistor Colour Code

Fundamentals

Read the value from the bands, or find the bands for a value.

Inputs

Results

Resistance

Not judged: reading bands is a lookup. The tolerance band gives the spread; a meter settles it.
270Ω
Tolerance
± 5%
Range
257Ω … 284 Ω

Start from the band nearest a lead; the tolerance band often stands apart. Gold and silver are never a first digit. If in doubt, measure.

redvioletbrowngold

Band order

The principle

The colour code gives significant digits and a power-of-ten multiplier: two digits on 4-band parts, three on 5- and 6-band parts. Tolerance follows, and on 6-band parts the temperature coefficient.

4-band
R=(10d1+d2)×10 m  ±  tolR = (10 d_1 + d_2)\times 10^{\,m} \;\pm\; \t{tol}
5- and 6-band
R=(100d1+10d2+d3)×10 m  ±  tolR = (100 d_1 + 10 d_2 + d_3)\times 10^{\,m} \;\pm\; \t{tol}
The 6th band adds the temperature coefficient in ppm/°C.
  • d1d2d3d_1 d_2 d_3significant digits, read from the colours
  • mmmultiplier exponent (gold = −1, silver = −2)
  • tol\t{tol}tolerance band: brown ±1 %, red ±2 %, gold ±5 %, silver ±10 %
More detail

The digits

Black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. Red to violet runs in rainbow order.

At the bench

  • No tolerance band means ±20 % (older parts).
  • A single black band marks a zero-ohm link, typically rated 1–2 A.
  • Pigments shift with age and heat. Confirm with a meter.
  • SMD parts print digits instead: 472 = 47×10² = 4.7 kΩ, 4701 = 4.70 kΩ, and EIA-96 01C = 100×100 = 10 kΩ.
Reference: IEC 60062, marking codes for resistors and capacitors.

Engine version ⁨1.18.3⁩