Resistor Color Code Calculator
Pick the colour bands as they appear on the resistor and read off the resistance, tolerance and the range the real part can fall in.
How it works
The bands are read from the end where they are grouped most closely. On a 4-band resistor the first two are digits, the third multiplies them by a power of ten, and the fourth is the tolerance. A 5-band part gives three digits before the multiplier, which is how tighter-tolerance resistors express an extra significant figure.
Gold and silver do double duty. As a multiplier they divide rather than multiply — ×0.1 and ×0.01 — which is how values below 10 Ω are marked. As a tolerance band they mean ±5% and ±10%.
Tolerance is not a rounding note; it is the manufacturer's guarantee. A 4.7 kΩ resistor at ±5% may legitimately measure anywhere from 4,465 Ω to 4,935 Ω, and in a divider or timing circuit that spread is often the dominant source of error.
The formula
4-band
R = (digit1 digit2) × multiplier ± tolerance
5- and 6-band
R = (digit1 digit2 digit3) × multiplier ± tolerance
Tolerance range
min = R × (1 − t/100), max = R × (1 + t/100)
6th band
temperature coefficient in ppm/°C
How much the value drifts per degree — only marked on precision parts.
Worked examples
| Scenario | Working | Result |
|---|---|---|
| Yellow, violet, red, gold | 47 × 100, ±5% | 4.7 kΩ, 4,465 Ω to 4,935 Ω |
| Brown, black, black, brown, brown | 100 × 10, ±1% | 1 kΩ, 990 Ω to 1,010 Ω |
| Brown, black, gold, gold | 10 × 0.1, ±5% | 1 Ω — a gold multiplier divides |
When you'd use it
- Identifying an unlabelled resistor from a parts drawer
- Checking a part matches the value a schematic calls for
- Working out whether tolerance explains a measurement that looks off
- Learning the code while building or repairing a circuit
Common questions
Which end do I start reading from?
From the end where the bands sit closest together. The tolerance band is usually separated by a wider gap, and gold or silver is almost always the tolerance — so if you see gold at one end, it is the last band, not the first.
What if the colours are ambiguous or faded?
Measure it. Brown and red, and orange and yellow, are genuinely hard to tell apart on small or heat-aged parts. A multimeter takes two seconds and removes the doubt — decode the bands to confirm what you measured, not the other way round.
Why does my resistor measure a different value?
Within tolerance, that is expected and correct. Outside it, check that you are not measuring the resistor in-circuit — parallel paths on the board will read lower than the part itself. Lift one leg before measuring.
What does the sixth band mean?
Temperature coefficient in parts per million per °C. It only matters where the circuit sees a wide temperature range and the value must stay put — precision references, instrumentation. For general use you can ignore it.
Is anything I enter sent to a server?
No. Every calculation runs in your browser, so component values, circuit figures and measurements are never uploaded, logged or stored. There is no account and no record of what you typed.