Calculators
Resistor colour code calculator
By Bulan Sarkar
Pick the colours to get the resistance, or type a value to get the colours. It handles 3, 4, 5 and 6-band parts and shows the range the tolerance allows. When a value is not a standard one, it gives you the nearest value you can buy.
- Resistance
- 47 kΩ
- Tolerance
- ±5 %
- May measure
- 44.65 kΩ to 49.35 kΩ
A standard value: it is in E6, E12, E24.
How to read the bands
Start at the end where the bands sit close together. The tolerance band usually stands off on its own at the other end. Gold and silver never stand for a digit, so a part can never start with one of them.
On a four-band part the first two bands are digits, the third is a power-of-ten multiplier and the fourth is the tolerance. Five-band parts add a third digit before the multiplier, which is why the same colour in band 3 means something different on the two. A sixth band, where there is one, gives the temperature coefficient: how many parts per million the resistance moves for each kelvin of temperature change. Three bands and no tolerance band is an old convention for ±20 %.
The digits run black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. Gold and silver multiply by 0.1 and 0.01. The tolerance and temperature-coefficient colours here follow IEC 60062:2016; older precision parts and some charts use grey for ±0.05 % rather than ±0.01 %, so check the datasheet when the last digit of a precision part matters. The colour code lesson goes through the reading order, the common misreadings and why the code survives.
The tolerance range is the marked value plus and minus the percentage. Parts are sold in preferred-value series whose steps are spaced so that neighbouring tolerance bands just overlap: E24 for ±5 %, E96 for ±1 %. That is why this calculator checks the result against the series and offers the nearest value when yours is not in it. The E-series lesson explains the spacing and resistor tolerance covers what the percentage does and does not promise.
Worked examples
Reading a five-band part
A metal-film resistor reads orange, orange, black, brown, brown. Five bands, so three digits: orange 3, orange 3, black 0 give 330. The fourth band, brown, multiplies by 10, so the value is 330 × 10 = 3.3 kΩ. The last brown is ±1 %.
One per cent of 3.3 kΩ is 33 Ω, so a good part measures anywhere from 3.267 kΩ to 3.333 kΩ. Read it as a four-band part by mistake and orange, orange, black gives 33 × 1 = 33 Ω, a hundred times too small. The brown multiplier gets taken for a tolerance band and the last brown is left with nothing to do, which is the clue. Count the bands first.
Coding 4.99 kΩ, and why four bands cannot
4.99 kΩ has three significant digits. A four-band code has room for two, so the best it can do is 5 kΩ: green, black, red, gold. That is a different resistor, and 5 kΩ is not a stocked E24 value either; the nearest E24 part is 5.1 kΩ.
On five bands the value fits exactly. Yellow 4, white 9, white 9, then brown for ×10, then brown for ±1 %: yellow, white, white, brown, brown. 4.99 kΩ is an E96 value, which is the series 1 % parts come in, so this is the part a distributor will have on the shelf.
When the colours are hard to tell apart
Red against orange and brown against red are the usual confusions, and on the multiplier band either one moves the answer by a factor of ten. Old parts that have run hot go brown all over. If the answer looks wrong for where the part sits in the circuit, lift one leg and measure it with a multimeter. Surface-mount parts have no bands at all; their printed codes are in the SMD resistor codes lesson.