Resistor Color Code Calculator

About Resistor Color Code Calculator

Leaded resistors are too small to print a readable number on, so their value is painted as coloured bands. The scheme is set by the international standard IEC 60062: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. In the multiplier position the same colours mean powers of ten (brown ×10, red ×100 and so on), with gold for ×0.1 and silver for ×0.01.

The calculator reads 3-, 4-, 5- and 6-band resistors and also works in reverse: enter a value and tolerance and it gives the band colours. It accepts shorthand such as 4k7, 2R2 and 1M, and it tells you which E-series of preferred values, from E6 to E96, the result belongs to.

What each band means for each band count

Three bands: digit, digit, multiplier; with no tolerance band the part is ±20%. Four bands: digit, digit, multiplier, tolerance, the format of the ubiquitous ±5% carbon-film resistor. Five bands: three digits, multiplier, tolerance, used for precision parts of ±1% and better. Six bands: the five-band layout plus a temperature-coefficient band in ppm/K.

The number of significant digits is the real difference. 4.75 kΩ has three significant digits, so it cannot be written with four bands; it needs five (yellow, violet, green, brown, brown). Ask this calculator for a four-band code for 4750 Ω and it will tell you it cannot be represented.

Which end do you start from?

Gold and silver are never digits, so if one end is gold or silver, that is the tolerance end on the right. The tolerance band is also usually set a little apart from the others. Five-band precision resistors are the tricky case: with brown (±1%) as the tolerance, both ends can be brown. Brown, black, black, brown, brown is 1 kΩ ±1%, but read backwards it is brown, brown, black, black, brown, which is 110 Ω ±1%. Both are legitimate standard values, so the colours alone cannot settle it.

Look at the spacing, and if it is still unclear, measure with a multimeter. On blue-bodied metal-film resistors, red, orange and brown are easy to confuse under warm light; check under bright white light.

How tolerance and preferred values fit together

Resistor values come in uneven steps such as 10, 15, 22, 33, 47, 68 because they are tied to tolerance. For ±20% parts you only need enough values per decade that neighbouring tolerance ranges just meet, and six (E6) is enough. ±10% needs twelve (E12), ±5% twenty-four (E24) and ±1% ninety-six (E96). These series are defined in IEC 60063.

That makes the E-series result a handy sanity check. 4.7 kΩ is an E6 value and about the most common resistor there is; 4.3 kΩ is E24; 4.75 kΩ is E96. If you decode something like 4.8 kΩ, which belongs to no series, you have most likely misread a colour.

Tolerance colours in IEC 60062 and in this calculator

According to Vishay's colour card, drawn up to IEC 60062, the tolerance colours are silver ±10%, gold ±5%, red ±2%, brown ±1%, green ±0.5%, blue ±0.25%, violet ±0.1%, orange ±0.05%, yellow ±0.02% and grey ±0.01%. This calculator follows that table: you can pick the ultra-precision orange (±0.05%) and yellow (±0.02%) tolerance bands, and grey is read as ±0.01%. Some older charts list grey as ±0.05%, so for precision parts confirm the grade from the datasheet as well.

The sixth band: temperature coefficient

The temperature coefficient states how many parts per million the resistance changes per kelvin (or degree Celsius). IEC 60062 assigns brown 100, red 50, yellow 25, orange 15, blue 10 and violet 5 ppm/K. At 100 ppm/K, a 100 °C change shifts the value by 1%.

A 330 Ω resistor rated 50 ppm/K that warms from 25 °C to 75 °C changes by 50 × 50 = 2,500 ppm, or 0.25%, about 0.8 Ω. That sits comfortably inside a ±1% tolerance, but in measuring instruments or reference voltage dividers, where a ratio must hold as the temperature changes, the tempco band matters as much as the tolerance band.

Worked examples

How to use it

1. Choose the number of bands (3 to 6) and pick colours starting from the left.
2. The value, tolerance range and temperature coefficient appear immediately.
3. To go the other way, enter a value such as 4k7 and a tolerance to get the bands.

Frequently asked questions