Resistor Color Code Calculator

Decode a resistor's colour bands into its resistance and tolerance. Choose 4-band or 5-band, pick each colour, and get the value in ohms — with the meaning of every band shown.

How to use this calculator

Choose 4-band or 5-band (5-band resistors have an extra digit for precision).
Select each band's colour in order, from the end opposite the tolerance band.
For 4-band, the Band 3 field is ignored. Press Decode.

Formula used

Resistance = (significant digits) × multiplier, ± tolerance

First two (or three) bands are digits; the next is a power-of-ten multiplier; the last is tolerance. Brown-Black-Red = digits 1,0 × 100 = 1,000 Ω = 1 kΩ. Read from the end where bands are grouped closest, with the tolerance band set slightly apart.

Example calculation

Worked example

Brown-Black-Red-Gold (4-band): digits 1 and 0 = 10, × 100 = 1,000 Ω = 1 kΩ, ±5%.

The ±5% means the real resistor is anywhere from 950 Ω to 1,050 Ω — which is fine for most circuits.

Reading the rings

Resistors are too small to print numbers on, so their value is encoded in coloured bands using a scheme every electronics hobbyist eventually memorises (the mnemonic "Bad Beer Rots Our Young Guts But Vodka Goes Well" gives the digit order black-brown-red-...). Four-band resistors give two significant digits plus a multiplier; five-band add a third digit for tighter-tolerance precision parts.

The two things that trip up beginners: reading direction (start from the end where the bands cluster; the lone tolerance band, usually gold or silver, marks the other end) and the tolerance itself — a 1 kΩ ±5% resistor can measure anywhere in a 100 Ω-wide window, so a multimeter reading that's slightly off the nominal value is normal, not a fault.

Why use this calculator?

Decode any 4- or 5-band resistor without memorising the colour chart.
See the tolerance range, so a slightly-off meter reading doesn't alarm you.
Values shown in Ω, kΩ and MΩ automatically.

Frequently asked questions

How do I read a resistor colour code?

Hold it with the tolerance band (usually gold or silver, set slightly apart) on the right. Read left to right: the first bands are digits, the next is a multiplier (power of ten), the last is tolerance. Brown-black-red = 10 × 100 = 1,000 Ω.

What's the difference between 4-band and 5-band resistors?

4-band gives two significant digits plus a multiplier and tolerance; 5-band adds a third significant digit for greater precision. 5-band resistors are typically used where tighter tolerance (±1% or better) matters.

Which end do I start reading from?

From the end where the bands are grouped closest together. The tolerance band sits slightly apart at the other end, and is often gold (±5%) or silver (±10%). If in doubt, the value that gives a standard resistor value is usually the right reading direction.