What does this calculator do?
Through-hole (axial) resistors show their value with color bands. On a four-band resistor, the first two bands are significant digits, the third is the multiplier and the fourth is the tolerance.
R = (10×B1 + B2) × multiplier
Read the resistor starting from the end opposite the tolerance band, which is usually set slightly apart. Turn the first two bands into digits, apply the multiplier and then read the tolerance.
Worked example
Yellow, violet, red and gold is 47 × 100 = 4700 Ω, that is, 4.7 kΩ ±5 %.
Practical tips
- A gold band usually means ±5 % and a silver band ±10 %.
- Five- and six-band resistors use an extra significant digit and sometimes a temperature coefficient band.
- Measure with a multimeter if the part is damaged or the colors are hard to tell apart.
Common mistake to avoid
Read from the correct end: starting from the tolerance band gives a completely different value.
How a resistor’s color code works
The color code is an international standard (IEC 60062). Each color stands for a digit from 0 to 9, and the band’s position tells you whether it is a digit, a multiplier or a tolerance:
- 4 bands: R = (10 · B1 + B2) × multiplier; the fourth band is the tolerance.
- 5 bands: R = (100 · B1 + 10 · B2 + B3) × multiplier; the fifth band is the tolerance. Used on precision resistors (±1 % or better).
- 6 bands: like 5 bands, plus a sixth band giving the temperature coefficient in ppm/K.
- Tolerance range: Rmin = R · (1 − t) and Rmax = R · (1 + t).
Where to start reading: the tolerance band (gold, silver, or brown on precision parts) is usually set further apart from the others, and the first band is usually closer to one end.
Color code table
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | × 1 | — |
| Brown | 1 | × 10 | ±1 % |
| Red | 2 | × 100 | ±2 % |
| Orange | 3 | × 1 k | — |
| Yellow | 4 | × 10 k | — |
| Green | 5 | × 100 k | ±0.5 % |
| Blue | 6 | × 1 M | ±0.25 % |
| Violet | 7 | × 10 M | ±0.1 % |
| Grey | 8 | × 100 M | — |
| White | 9 | × 1 G | — |
| Gold | — | × 0.1 | ±5 % |
| Silver | — | × 0.01 | ±10 % |
| No band | — | — | ±20 % |
Orange, yellow and grey tolerances exist in the standard but are rare on commercial resistors, so they are left out here.
Common values and their colors
| 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 |
| 330 Ω | orange, orange, brown, gold | orange, orange, 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 |
| 47 kΩ | yellow, violet, orange, gold | yellow, violet, black, red, brown |
| 100 kΩ | brown, black, yellow, gold | brown, black, black, orange, brown |
Worked examples
Four bands: yellow, violet, orange, gold. Digits 4 and 7 → 47; orange multiplier × 1000 → 47 000 Ω = 47 kΩ; gold → ±5 %. The real value can be anywhere from 44.65 kΩ to 49.35 kΩ.
Five bands: brown, black, black, brown, brown. Digits 1, 0, 0 → 100; brown multiplier × 10 → 1000 Ω = 1 kΩ; brown tolerance → ±1 %, so between 990 Ω and 1010 Ω.
Low values: brown, black, gold, gold = 10 × 0.1 = 1 Ω ±5 %.
Common mistakes
- Reading it backwards: starting from the tolerance band gives an absurd or non-existent value; check that the result belongs to the E12 or E24 series.
- Confusing brown, red and orange: in poor light they look alike. When in doubt, measure with a multimeter.
- Confusing 4- and 5-band parts: on a 5-band resistor the fourth band is the multiplier, not the tolerance.
- Measuring in circuit: other components in parallel change the reading; disconnect at least one lead.
Frequently asked questions
Which resistor values exist?
They are made in E series. E12 (±10 %) uses 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68 and 82 times powers of ten. E24 (±5 %) adds in-between values such as 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75 and 91.
How do I read SMD resistors?
With a number code: in “103” the first two digits are the value and the third is the number of zeros, 10 × 10³ = 10 kΩ. The letter R marks the decimal point: “4R7” = 4.7 Ω.
Which resistor does my circuit need?
Work it out first with Ohm’s law or, for an LED, with the LED resistor calculator, then look up its colors here.
For the origin of the code, mnemonics and how to read doubtful resistors, see the color code guide.
Educational tool. Check tolerances, datasheets, standards and real operating conditions before using the results in critical applications.