The small resistors on a circuit have color bands painted on them instead of numbers. Pick the colors in the calculator above and it reads out the resistance and tolerance right away, and if you enter the resistance you want, it tells you which color bands to look for. If you learn the reading rules once before using the calculator, you can read most resistors without it.
How to use it
- Color bands → resistance: choose the number of bands (4-band or 5-band), then select the colors painted on the resistor in order from the front. The last band is the tolerance.
- Resistance → color bands: enter a resistance such as
4.7k,330,1M, or4k7and choose a tolerance, and it gives you the order of the color bands. A value that a 4-band resistor cannot show exactly (for example, 4.75 kΩ) is changed to the nearest value; in that case, choose 5 bands.
What each color means
| 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% |
Choosing the reading direction
A resistor gives a completely different value depending on which end you read from, so decide the starting direction first.
- If there is a gold or silver band, that band is the last one (the tolerance). Start reading from the opposite end.
- The tolerance band is often spaced a little farther from the other bands.
- Gold and silver cannot be in a digit position. If the first band is gold or silver, you are reading it backwards.
4-band vs. 5-band
- 4-band: 2 digits + 1 multiplier + 1 tolerance. The resistance is
(first two digits) × multiplier. The most common carbon film resistors (±5% tolerance) are this type. - 5-band: 3 digits + 1 multiplier + 1 tolerance. Often used for metal film resistors (±1% tolerance), which mark the value in finer detail.
Examples
| Color bands | Calculation | Resistance |
|---|---|---|
| Brown-black-red-gold | 10 × 100 | 1kΩ ±5% |
| Yellow-violet-orange-gold | 47 × 1,000 | 47kΩ ±5% |
| Red-red-brown-silver | 22 × 10 | 220Ω ±10% |
| Brown-black-black-brown-brown | 100 × 10 | 1kΩ ±1% |
| Green-blue-red-red-brown | 562 × 100 | 56.2kΩ ±1% |
A more detailed explanation of reading color bands and of the standard value series (E12 and E24) is in the guide to reading resistors.