The colored stripes on a resistor are a compact code for its resistance and precision. Once you know that the first bands are digits, the next is a multiplier, and the last is tolerance, any resistor becomes readable at a glance.
The color-to-number chart
Every color maps to a digit and to a power-of-ten multiplier. This one table drives the whole system:
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | — |
| Yellow | 4 | ×10k | — |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | ×100M | ±0.05% |
| White | 9 | ×1G | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Reading a 4-band resistor
This is the most common type. The four bands are: digit, digit, multiplier, tolerance.
Example — brown, black, red, gold:
- Brown = 1, Black = 0 → significant digits 10
- Red multiplier → ×100
- 10 × 100 = 1,000 Ω = 1 kΩ
- Gold → ±5% tolerance
Reading a 5- and 6-band resistor
A 5-band resistor adds a third significant digit before the multiplier — digit, digit, digit, multiplier, tolerance — for tighter-tolerance parts. A 6-band resistor adds one more stripe for the temperature coefficient (how much the value drifts per °C), important in precision and high-temperature designs.
Which end to start from
The tolerance band is usually printed slightly farther from its neighbors, and gold/silver are almost always tolerance. Put that gap on the right and read left-to-right. If you read it backwards you will usually get an absurd value (like 91 GΩ), which is a quick sanity check that you have the orientation flipped.
Why the values look “odd”
Resistors come in standard series (E12, E24, E96…) chosen so that, with tolerance, the ranges tile the number line with no gaps. That is why you see 4.7 kΩ and 6.8 kΩ rather than round 5 kΩ or 7 kΩ — the spacing is logarithmic, sized to each tolerance band.
Surface-mount (SMD) resistors: numbers, not colours
The colour code is for through-hole resistors with wire legs. The tiny black rectangles on modern circuit boards — surface-mount resistors — are far too small for bands, so they use a printed numeric code that follows the same digit-then-multiplier logic:
- 3-digit — first two digits are significant, the third is the number of zeros.
472= 47 followed by two zeros = 4,700 Ω (4.7 kΩ). - 4-digit (tighter tolerance) — three significant digits plus a multiplier.
4701= 470 + one zero = 4,700 Ω. - R for the decimal point — used for values under 10 Ω.
4R7= 4.7 Ω,R47= 0.47 Ω. - EIA-96 — on 1% parts, two digits give a lookup code and a letter gives the multiplier, packing three significant figures into three characters.
So the same mental model — significant figures, then a multiplier — carries across both systems; only the notation changes.
Always cross-check the value
Colours fade, parts get mismarked, and a resistor pulled from a drawer may not be what the label said. Treat the colour code as a strong hint, not gospel: for anything that matters, confirm the value with a multimeter on its resistance range. The code tells you the nominal value and tolerance; the meter tells you what the part actually is right now, which can differ if it has been overheated or damaged.
Frequently asked questions
Which end do I read from?
Start from the band closest to an edge. The tolerance band (often gold or silver) sits slightly apart and goes on the right, so you read toward it.
What is the difference between 4-band and 5-band resistors?
A 4-band resistor has 2 significant digits; a 5-band has 3, giving finer precision. 5- and 6-band parts are typical for 1% and tighter tolerances.
What does the gold band mean?
As a multiplier, gold means ×0.1; as a tolerance band it means ±5%. Position tells you which role it plays — multipliers sit before the gap, tolerance after.
How do I read tiny surface-mount (SMD) resistors?
SMD resistors use printed numbers, not colours. A 3- or 4-digit code works like the colour bands: the last digit is the number of zeros (e.g. 472 = 4,700 Ω). A code with an R marks the decimal point (4R7 = 4.7 Ω). The EIA-96 system uses two digits plus a letter for 1% parts.
Why do my bands look brown and red but the value seems wrong?
Reading from the wrong end is the usual cause — the value reverses. Also, on older or heated resistors the colours can fade or discolour (red can look brown, orange can look yellow). When in doubt, measure it with a multimeter and use the colour code as a cross-check.
What is the temperature-coefficient band on a 6-band resistor?
The sixth band gives the temperature coefficient in parts per million per °C (ppm/°C) — how much the resistance drifts as it heats up. Brown is 100 ppm/°C, red 50, and so on. It matters for precision circuits where small drifts affect the result.