Resistor colour code calculator

The bands on a resistor are the part number. Two or three of them spell out the digits, the next one says how many zeros to hang on the end, and the one set slightly apart from the rest says how far the real part is allowed to stray from that figure. Read them with the tolerance band on the right — gold and silver almost always sit there, which is the easiest way to work out which end you are starting from.

How it is calculated

resistance = digits × multiplier · range = resistance ± tolerance

Each digit colour also carries a multiplier one decade above the previous one, which is why black is 1 and white is a billion. Gold and silver break the pattern: they carry no digit at all and their multipliers are fractions, so a gold third band divides by ten instead of multiplying.

Source: Vishay — Color Code and Standard Resistance Series, document 20143 (rev. 28-Aug-09): digit, multiplier and tolerance columns

Questions people ask

Which end do I start reading from?

From the end where the bands are evenly spaced. The tolerance band sits slightly apart from the others and is very often gold or silver — neither of which can be a digit, so if you see one, you have found the far end. When both ends look alike, the reading that gives a value from the standard series is the right one; the other will land on a number no one manufactures.

Why does my resistor measure a different value?

Because the bands promise a range, not a number. A 1 kΩ resistor with a gold band is allowed anywhere between 950 Ω and 1050 Ω and is still within specification. The range is on this page for exactly that reason. A reading outside it means either a misread band or a part that has been cooked.

What does the sixth band mean?

The temperature coefficient, in parts per million per kelvin. Brown, the most common, means 100 ppm/K: a 10 kΩ resistor drifts by one ohm for every kelvin. It only appears on precision parts, and only ever as the sixth band — the same colour anywhere else in the code means a digit or a multiplier.

Are four and five-band resistors different parts?

They come from different series. Four bands carry two significant figures and come from E12 or E24, the series with 5% and 10% steps. Five and six bands carry three figures and come from E48, E96 or E192, where the steps are tight enough that the third digit actually says something.

Where do these colours come from?

From the chart the manufacturers print, which follows IEC 60062. The figures on this page are transcribed from Vishay's own colour code document rather than reconstructed, including the temperature coefficients, which vary more between makers than the digits do.

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