Cert ID: Q/50404

How to read a resistor colour code.

Typically resistors will come in one of two types; four band or five band.

The first thing to do when reading the code is to decide which end is the start. You will find that the bands on the resistor will be arranged as a single band (the tolerance band) towards one end and the remaining bands grouped together at the other end. With the single band to your right, the code is read from the leftmost band as shown below.

Four band resistors

The two leftmost bands give the first two digits of the resistors value. The third band is the multiplier which is applied to the value obtained from the first two bands. The column named band 3 in the table is not read for four band resistors.  The fourth band on the resistor represents the resistors tolerance. See the worked examples below the table. If no tolerance band is shown then the tolerance is 20%.

Five band resistors

In this case the three leftmost bands give the first three digits of the resistors value and the fourth band represents the multiplier. The tolerance is read from the fifth band of the resistor. See the worked examples below the table.

Examples

A four band resistor is coded as red, violet, orange, silver. The first two bands, red and violet, give us the value 27. The third band, orange, represents a multiplier of 1k. The resistors value is therefore 27 x 1K = 27K ohms. The fourth band, silver, gives us a tolerance of ± 10%.

A five band resistor is coded red, orange, violet, black, brown. In this case the first thre bands give us the resistor value as 237 and the fourth band, black, gives us a multiplier of 1. The full value of this resistor is therefore 237 x 1 = 237 ohms. The fifth band, brown, gives us a tolerance of ± 1%.

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