About this calculator
Through-hole resistors carry their value as coloured bands rather than printed digits, because the stripes stay readable whichever way the part is soldered in. This calculator translates between the two directions: pick the band colours to read a resistance, or enter a resistance to see which bands it should carry.
It handles both the common 4-band scheme (two digits, a multiplier and a tolerance) and the 5-band scheme used for precision parts (three digits, a multiplier and a tolerance).
How it works
Each colour maps to a digit from 0 to 9, following the spectrum: black is 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8 and white 9. The first bands spell out the significant figures of the value.
The next band is the multiplier — the same colour scale, but read as a power of ten. Orange as a multiplier means ×1000, not the digit 3. Gold and silver extend the scale downwards, meaning ×0.1 and ×0.01 for sub-10 Ω resistors.
The final band, usually set slightly apart from the rest, is tolerance. Gold is ±5% and silver ±10%, the two you will meet most often. Brown (±1%) and red (±2%) appear on precision parts, which are also the ones that tend to use five bands.
Reading direction matters: hold the resistor with the tolerance band on the right. The tolerance band is usually gold or silver and sits with a wider gap before it.
Worked example
A 4-band resistor banded brown, black, orange, gold.
- Brown = 1, black = 0 → significant digits 10
- Orange as multiplier = ×1000
- R = 10 × 1000 = 10000 Ω = 10 kΩ
- Gold = ±5% → anywhere from 9.5 kΩ to 10.5 kΩ
A 10 kΩ ±5% resistor — the single most common value in hobby electronics.
Practical notes
- Read with the tolerance band on the right. Reading a 4-band resistor backwards turns brown-black-orange-gold into gold-orange-black-brown, which decodes to nonsense — a useful sign you have it the wrong way round.
- Brown, red, orange and gold are hard to tell apart on a small part under warm light. When it matters, measure with a multimeter.
- Resistors only come in preferred values (E12, E24, E96), so not every number you calculate exists as a part. If your answer is 2.9 kΩ, the shelf has 2.7 kΩ and 3.0 kΩ.
- A tolerance band that is missing entirely means ±20%, an old convention you will only see on vintage equipment.
- Surface-mount resistors use printed numeric codes instead of bands — the SMD resistor code decoder handles those.
Frequently asked questions
How do I read a 4-band resistor?
First two bands are digits, third is the number of zeros to add, fourth is tolerance. Brown-black-red-gold is 1, 0, then two zeros: 1000 Ω, ±5%.
Which end do I start reading from?
The end furthest from the tolerance band. That band is typically gold or silver and separated from the others by a wider gap. If both ends look the same, measure it.
What is the difference between 4-band and 5-band?
A 5-band resistor gives three significant digits instead of two, so it can express tighter values like 4.99 kΩ. Five bands usually signals a 1% or better part.
What do gold and silver mean as the third band?
As a multiplier rather than a tolerance, gold means ×0.1 and silver ×0.01. That is how values below 10 Ω are expressed — brown-black-gold is 1.0 Ω.
Why does my resistor measure slightly off?
Tolerance. A 10 kΩ ±5% part is in spec anywhere between 9.5 kΩ and 10.5 kΩ. Your meter also has its own error, and measuring a resistor while it is soldered into a circuit reads the whole network, not the one part.