Reading resistor colour codes
Through-hole resistors are still marked with coloured bands because the marking survives heat, solder and decades of use. The system is positional: the first bands are digits, the next band is a power of ten, and the band that sits apart at the other end is the tolerance. Read them left to right from the end where the bands are closest together.
The four, five and six band versions
- 4 band: digit, digit, multiplier, tolerance. Brown, black, red, gold = 1, 0, ×100, ±5% = 1 kΩ ±5%.
- 5 band: digit, digit, digit, multiplier, tolerance — used for ±1% and better parts. Brown, black, black, brown, brown = 100 × 10 = 1 kΩ ±1%.
- 6 band: as 5 band plus a temperature coefficient in ppm/K. Brown, black, black, brown, brown, red = 1 kΩ ±1%, 50 ppm/K.
The full chart
| Colour | Digit | Multiplier | Tolerance | Temp. coefficient |
|---|---|---|---|---|
| Black | 0 | ×10^0 | — | — |
| Brown | 1 | ×10^1 | ±1% | 100 ppm/K |
| Red | 2 | ×10^2 | ±2% | 50 ppm/K |
| Orange | 3 | ×10^3 | — | 15 ppm/K |
| Yellow | 4 | ×10^4 | — | 25 ppm/K |
| Green | 5 | ×10^5 | ±0.5% | — |
| Blue | 6 | ×10^6 | ±0.25% | 10 ppm/K |
| Violet | 7 | ×10^7 | ±0.1% | 5 ppm/K |
| Grey | 8 | ×10^8 | ±0.05% | — |
| White | 9 | ×10^9 | — | — |
| Gold | — | ×0.1 | ±5% | — |
| Silver | — | ×0.01 | ±10% | — |
Memory aid: black through white runs 0 to 9 in rainbow order, with brown and red at the start. Gold and silver on their own are never digits — they are the ×0.1 and ×0.01 multipliers, and they are also tolerance colours, which is why they only appear at the end of a resistor.
The backwards-reading trap
Two of the three "end" bands of a 4-band resistor are usually gold or silver, and those can never be a first digit, so you can normally tell which end to start from. The trap appears with 5- and 6-band parts, where both ends may look like valid low digits — for example a 220 Ω 5-band resistor read backwards looks like a plausible 10 kΩ part. Three defences: the tolerance band sits slightly apart, the colour at the end of the chain rarely appears at the start of a real series value, and you almost always know roughly what value you expected.
Preferred values: why 4.7 kΩ and not 4.8 kΩ
Resistors are made in the E-series, spaced so that consecutive values differ by just over twice the tolerance. That makes every manufactured part usable: if a 5% part is high and the next one low, their tolerance windows still overlap, so nothing is wasted. The E12 series (12 values per decade) suits ±10% parts, E24 suits ±5%, and E96 suits ±1%. This is why you can buy 4.7 kΩ but not 4.8 kΩ — and why the calculator reports the nearest E24 value when your calculation lands in between.
Practical reading tips
- Orientation: the tolerance band is the one with a visible gap; start from the opposite end.
- Lighting: brown, red and orange are easy to confuse under warm light; check outdoors or with a cool white lamp.
- Sanity check: measure with a multimeter once the part is out of circuit — the colour code tells you the nominal value, not the actual one.
- Power rating is not in the code: a physically larger resistor is a higher-wattage one, and the body size (1/8 W to 5 W) is the only clue you get.
Frequently asked questions
How do I read a 4-band resistor?
Read from the end with the bands closest together: first band = first digit, second = second digit, third = multiplier (a power of ten), fourth = tolerance. Brown, black, red, gold is 1, 0, ×100, ±5% — a 1 kΩ resistor with 5% tolerance.
What is the difference between 4-band and 5-band resistors?
A 5-band resistor carries three significant digits instead of two, which is how ±1% and ±0.1% parts are marked. A 5-band brown-black-black-brown-brown is 100 × 10 = 1 kΩ ±1%; the equivalent 4-band part can only express 1 kΩ as a two-digit mantissa.
Which band is the tolerance band?
The one standing slightly apart from the others, usually at the right-hand end: gold is ±5%, silver ±10%, brown ±1%, red ±2%, green ±0.5%, blue ±0.25%, violet ±0.1% and no band at all ±20%. Because gold and silver are never digits, they also tell you which end to read from.
Why are resistors only made in values like 4.7 kΩ and 5.1 kΩ?
The E-series spacing guarantees that the tolerance windows of consecutive values overlap, so every part made can be sold. E12 gives 12 values per decade for ±10% parts, E24 gives 24 for ±5%, and E96 gives 96 for ±1%. If your calculated value falls between two of them, use the nearest standard part.
What does the 6th band mean?
It is the temperature coefficient in ppm per kelvin — how much the resistance drifts as the part heats or cools. Brown is 100 ppm/K, red 50, orange 15, yellow 25, blue 10 and violet 5. A 15 ppm/K part is far more stable in a circuit that heats up than a 100 ppm/K one.
Can I read the colour code on a burnt resistor?
Only if the body survived — heat usually darkens the bands, especially the brown and red ones. If the code is unreadable, measure a known-good identical board if you have one, measure the resistor out of circuit if it still shows a plausible value, or work backwards from the circuit: the voltage across it and the current through it give the resistance.