How to read resistor colour codes
Through-hole resistors are too small to print a value on, so the value is painted as coloured bands: two or three digits, a multiplier, a tolerance and sometimes a temperature coefficient. The code is the same on every resistor in the world (IEC 60062), and once you know ten colours and where to start you can read any of them. This calculator reads a code you pick band by band, or shows the bands for a value you type, and explains each band on a resistor drawn to scale.
How to use the resistor colour code calculator
- Colours → value: choose 3, 4, 5 or 6 bands, then set each band's colour from the lists on the left or by clicking the colour chips under the drawing. The value, tolerance window and series appear at once, and each band is labelled on the resistor.
- Value → colours: switch direction, type the resistance (4.7k, 4k7, 220, 1M, 0.47), pick the tolerance and whether you want the four-band or five-band code, and the bands to look for are drawn.
- Nearby values lists the standard E24 values from half to double yours with both codes, for when the one you read is not what you need; Calculation reads the code band by band; click the resistor for the other code and tips on direction.
The colour chart
| Colour | Digit | Multiplier | Tolerance | Temp. coefficient |
|---|---|---|---|---|
| Black | 0 | × 1 | — | 250 ppm/K |
| Brown | 1 | × 10 | ±1% | 100 ppm/K |
| Red | 2 | × 100 | ±2% | 50 ppm/K |
| Orange | 3 | × 1k | ±0.05% | 15 ppm/K |
| Yellow | 4 | × 10k | ±0.02% | 25 ppm/K |
| Green | 5 | × 100k | ±0.5% | 20 ppm/K |
| Blue | 6 | × 1M | ±0.25% | 10 ppm/K |
| Violet | 7 | × 10M | ±0.1% | 5 ppm/K |
| Grey | 8 | × 100M | ±0.01% | 1 ppm/K |
| White | 9 | × 1G | — | — |
| Gold | — | × 0.1 | ±5% | — |
| Silver | — | × 0.01 | ±10% | — |
| None | — | — | ±20% | — |
The digit colours run black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9 — the order of the rainbow after the first three. A common mnemonic is Bad Boys Race Our Young Girls But Violet Generally Wins; make your own if that one does not stick.
Reading a resistor
- Find the end. The tolerance band is gold or silver on most parts, and sits a little apart from the rest. Hold the resistor so that band is on the right.
- Read the digits from the left: two on a four-band part, three on a five- or six-band part. Write them side by side.
- Apply the multiplier: the next band says how many zeros to add (or gold ÷10, silver ÷100).
- Read the tolerance and, on six-band parts, the temperature coefficient.
Colours fade and lighting lies: red and orange, brown and violet, blue and green are the usual confusions. If the result is not a standard value, you have probably swapped one of those, or read from the wrong end — try both directions and see which one lands on a standard value.
Four, five and six bands
Four bands are the everyday 5% (gold) and 10% (silver) carbon-film parts: two digits and a multiplier. Five bands give three digits, so values like 4.75 kΩ can be shown; they are the 1% (brown) and 2% (red) metal-film parts, usually on a blue body. Six bands add the temperature coefficient. Three bands are old 20% parts with no tolerance band. The trap is that a five-band 4.7 kΩ 1% reads yellow, violet, black, brown, brown: the black is the third digit (470), the brown the multiplier (×10) — the same colours in the four-band way of thinking would say 47 Ω.
| Value | 4 bands (5%) | 5 bands (1%) |
|---|---|---|
| 10 Ω | Brown, black, black, gold | Brown, black, black, gold, brown |
| 220 Ω | Red, red, brown, gold | Red, red, black, black, brown |
| 1 kΩ | Brown, black, red, gold | Brown, black, black, brown, brown |
| 4.7 kΩ | Yellow, violet, red, gold | Yellow, violet, black, brown, brown |
| 10 kΩ | Brown, black, orange, gold | Brown, black, black, red, brown |
| 100 kΩ | Brown, black, yellow, gold | Brown, black, black, orange, brown |
| 1 MΩ | Brown, black, green, gold | Brown, black, black, yellow, brown |
Standard values: the E series
Resistors come in preferred values spaced so that the tolerance windows just touch: E12 for 10% parts (10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82), E24 for 5% (adding 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75, 91), E96 for 1% (every 2.4%). Every decade repeats the pattern, so 4.7 Ω, 47 Ω, 470 Ω, 4.7 kΩ and 4.7 MΩ all exist. A colour code that decodes to 450 Ω has almost certainly been misread, because nobody makes 450 Ω; the calculator tells you which series a value belongs to, or that it belongs to none.
Your resistor
- Bands: Yellow, violet, red, gold.
- Value: 4.7 kΩ, ±5%, so between 4.465 kΩ and 4.935 kΩ.
- Series: a standard E6 value.
Worked example: yellow, violet, red, gold
Gold is the tolerance band, so it goes on the right. Yellow = 4 and violet = 7 give 47; red means two zeros, ×100, so 47 × 100 = 4.7 kΩ; gold is ±5%, so the real part is between 4.465 kΩ and 4.935 kΩ. 4.7 kΩ is in the E12 series, as expected for a 5% part. The same resistor as a 1% metal-film part would read Yellow, violet, black, brown, brown.
Questions
What if there is no gold or silver band?
Then it is a 1% or 2% part with brown or red as the tolerance, or an old three-band 20% part. Look for the wider gap before the last band, and try both directions: only one gives a standard value.
Why do surface-mount resistors have numbers instead?
SMD parts are flat enough to print on: 472 means 47 × 10² = 4.7 kΩ, the same idea as the bands; 4R7 means 4.7 Ω; four-digit codes (4701) are 1% parts with three digits and a multiplier. The LED resistor calculator and the others here show band colours for the values they suggest.
Does the body colour mean anything?
Only by convention: tan or beige bodies are usually carbon film (5%), blue bodies metal film (1%), and green or grey bodies often wire-wound or fusible types. Always read the bands.
What is the fifth band on a four-band resistor that has one?
Some military and fusible resistors carry an extra band for reliability or failure mode, set apart from the code. If a fifth band is white, salmon or an odd colour, ignore it and read the first four.