A resistor color code is a way of printing a number on a part that is too small and too round for legible text. Each color stands for a digit from 0 to 9, and the position of a band tells you what to do with that digit: use it as part of the value, as a power-of-ten multiplier, as a tolerance or as a temperature coefficient. The scheme is defined by the IEC 60062 standard, and it is the same on a beige carbon film resistor from a starter kit as on a blue metal film part from a distributor.
What each band position means
You will meet four layouts. Count the bands first, because the count decides how the rest of the code is read.
- 3 bands: digit, digit, multiplier. There is no tolerance band, which means ±20%. These turn up mostly in old radios and amplifiers.
- 4 bands: digit, digit, multiplier, tolerance. This is the usual layout for ±5% carbon film resistors, the kind sold in mixed kits for breadboard work.
- 5 bands: digit, digit, digit, multiplier, tolerance. The third digit allows values such as 4.99 kΩ or 10.2 kΩ, so this layout is used on ±1% and tighter parts.
- 6 bands: the 5-band code plus a sixth band for the temperature coefficient, which tells you how much the value shifts as the part warms up.
The arithmetic never changes. Write the digit bands side by side as a whole number, then multiply by the value of the multiplier band. Red, red, brown on a 4-band part is 22 × 10 = 220 Ω. The tolerance band then tells you how far the real resistance may sit from that nominal figure.
The complete color table
The digit column is the one worth memorizing. The multiplier follows directly from it: a multiplier band whose digit is N means "add N zeros", so orange (3) means ×1,000 and green (5) means ×100,000. Gold and silver are the exceptions; as multipliers they divide by 10 and by 100.
| Color | Digit | Multiplier | Tolerance | Temp. coefficient |
|---|---|---|---|---|
| Black | 0 | ×1 | – | 250 ppm/K |
| Brown | 1 | ×10 | ±1% (F) | 100 ppm/K |
| Red | 2 | ×100 | ±2% (G) | 50 ppm/K |
| Orange | 3 | ×1k | ±0.05% (W) | 15 ppm/K |
| Yellow | 4 | ×10k | ±0.02% (P) | 25 ppm/K |
| Green | 5 | ×100k | ±0.5% (D) | 20 ppm/K |
| Blue | 6 | ×1M | ±0.25% (C) | 10 ppm/K |
| Violet | 7 | ×10M | ±0.1% (B) | 5 ppm/K |
| Grey | 8 | ×100M | ±0.01% (L) | 1 ppm/K |
| White | 9 | ×1G | – | – |
| Gold | – | ×0.1 | ±5% (J) | – |
| Silver | – | ×0.01 | ±10% (K) | – |
| No band | – | – | ±20% (M) | – |
A tidy mnemonic for the digit order is "Better Be Right Or Your Great Big Venture Goes Wrong": black, brown, red, orange, yellow, green, blue, violet, grey, white. It also helps to notice that red through violet (2 to 7) runs in rainbow order. Black is nothing, brown sits just before red, and the two palest colors, grey and white, take the top two digits. A printed resistor color code chart taped above the bench saves looking it up while you learn.
Which end to start from
Reading from the wrong end gives a confident but wrong answer, so settle the direction before decoding anything. These clues, roughly in order of reliability, settle it on almost every part:
- Gold or silver goes on the right. Neither color is a digit, so neither can be the first band. On a 4-band part, a gold or silver band at one end is the tolerance band, and you start from the other end.
- Look for the gap. Most manufacturers leave a wider space before the tolerance band, or bunch the value bands toward one end of the body.
- Black never comes first. A leading zero would be pointless, so if one end band is black, start from the other end.
- Check the result against standard values. Resistors are made in the preferred values of the E-series, so a reading such as 5.7 kΩ or 23 kΩ suggests a misread color or the wrong starting end.
Five-band precision parts are the hardest case, because their tolerance band is usually brown (±1%) or red (±2%), and both of those colors are also valid first digits. Take a 10 kΩ ±1% resistor coded brown, black, black, red, brown. Read backwards it becomes brown, red, black, black, brown, which decodes to 120 × 1 = 120 Ω ±1%, and 120 Ω is a perfectly ordinary value. Here the gap is your best clue, and a quick check with a meter settles it in seconds.
Worked examples
220 Ω, 4 bands
Red (2), red (2), brown (×10), gold (±5%). The value is 22 × 10 = 220 Ω, and ±5% allows anything from 209 Ω to 231 Ω. This is the resistor many Arduino tutorials put in series with an LED on a 5 V pin; the 220 Ω resistor page shows its 5-band and SMD codes.
4.7 kΩ, 4 bands
Yellow (4), violet (7), red (×100), gold (±5%). That gives 47 × 100 = 4,700 Ω, written 4.7 kΩ or 4k7, with a tolerance window of 4,465 Ω to 4,935 Ω. It is the usual pull-up value on an I²C bus; see the 4.7 kΩ page for the equivalents.
10 kΩ, 5 bands
Brown (1), black (0), black (0), red (×100), brown (±1%). Three digits make 100, and 100 × 100 = 10,000 Ω. At ±1% the real value should fall between 9.9 kΩ and 10.1 kΩ. The same value on a 4-band ±5% part reads brown, black, orange, gold: there are only two digits, so the multiplier moves up one step to compensate. More codes for this value are on the 10 kΩ page.
0.47 Ω with a silver multiplier
Yellow (4), violet (7), silver (×0.01), gold (±5%) gives 47 × 0.01 = 0.47 Ω. With a gold multiplier instead (yellow, violet, gold, gold) the same digits give 4.7 Ω. Low values like these appear as current-sense resistors and as emitter resistors in audio power amplifiers. Whenever the third band of a 4-band part is gold or silver, the value is below 10 Ω. The 4.7 Ω page covers the gold-multiplier version.
A 6-band precision resistor
Yellow (4), white (9), white (9), brown (×10), brown (±1%), red (50 ppm/K). The value is 499 × 10 = 4,990 Ω, or 4.99 kΩ ±1%. The sixth band says the resistance changes by up to 50 parts per million for every kelvin of temperature change. If the board warms by 40 °C, the shift is at most 50 × 40 = 2,000 ppm, or 0.2%, which is about 10 Ω on this part. That matters in measurement and reference circuits and hardly at all in an LED indicator.
A 3-band resistor
Brown, black, orange with no fourth band is 10 × 1,000 = 10 kΩ at ±20%, so expect a measured value anywhere from 8 kΩ to 12 kΩ.
Faded, burnt and hard-to-read bands
Color reading is easiest in daylight or under a white LED lamp. Warm incandescent light pushes red, orange and brown toward each other, and the blue body of a metal film resistor makes blue, violet and grey bands harder to separate. The usual confusions are:
- red, orange and brown, especially on aged or heat-darkened parts;
- blue, violet and grey;
- white, grey and silver;
- gold and yellow or light brown, once the metallic paint has dulled.
Use the standard-value check as a tiebreaker. Suppose you read green, violet, red, gold. That decodes to 5.7 kΩ, which is not in any common series, while green, blue, red (5.6 kΩ) is one of the most common values made. The violet band is almost certainly blue. The guide to standard resistor values explains why only certain numbers are manufactured.
A resistor that has overheated is a different problem. Heat darkens the paint until every band looks brown, and the resistance itself may have drifted well away from its marking. Treat the colors on a scorched part as unreliable and get the value from the schematic, the parts list or an identical resistor elsewhere on the board.
Confirming the value with a multimeter
A meter check takes ten seconds and catches both misreads and damaged parts. A few habits make the reading trustworthy:
- Measure out of circuit. On a board, other components form parallel paths and the meter usually reads low. Lift one leg, or test the part before you solder it.
- Keep your fingers off both probe tips. Your body adds a resistance in parallel, often somewhere between hundreds of kilohms and a few megohms. That is negligible for a 220 Ω part but can pull a 1 MΩ reading down noticeably.
- Subtract lead resistance for low values. Touch the probes together first; a typical meter shows a few tenths of an ohm. On a 0.47 Ω resistor that offset is as large as the value you are trying to measure.
- Compare against the tolerance window, not the nominal value. A 4.7 kΩ ±5% part that reads 4.62 kΩ is in spec. One that reads 5.3 kΩ is either misread or faulty.
The meter has its own accuracy limit as well, often around ±1% plus a few counts on inexpensive models, so it cannot confirm that a 0.1% part is within tolerance.
Tools for the next resistor
Once you can read the bands by hand, the resistor color code calculator is a fast way to double-check a reading or to go the other way, from a value to its colors. Surface-mount parts use printed numbers instead of bands; the SMD resistor code guide and the SMD code calculator cover those.