Resistor color code calculator

How do I read a resistor color code?

Start from the end with the bands grouped together. On a 4-band resistor, the first two bands are digits, the third is the multiplier and the fourth the tolerance: yellow-violet-red-gold is 47 × 100 = 4.7 kΩ ±5%.

What do the colors stand for?

Black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, white 9. As a multiplier, gold is ×0.1 and silver ×0.01.

What about 5- and 6-band resistors?

They have three digit bands, then the multiplier and tolerance: red-yellow-white-orange-brown is 249 kΩ ±1%. A sixth band gives the temperature coefficient — red is 50 ppm/K.

What are the tolerance colors?

Brown ±1%, red ±2%, orange ±0.05%, yellow ±0.02%, green ±0.5%, blue ±0.25%, violet ±0.1%, grey ±0.01%, gold ±5%, silver ±10%; no band means ±20% (IEC 60062:2016).

What if the result looks wrong?

You may be reading from the wrong end. Tolerance bands are usually gold or silver, or set apart from the others; gold and silver never come first.

What is the range of values for a resistor with a stated tolerance?

Multiply the value by 1 ± tolerance. A brown-black-red-gold resistor is 1 kΩ ±5%, so a good part measures between 950 Ω and 1.05 kΩ.

How the bands are combined

The digit bands form a whole number, the multiplier band says by what power of ten to multiply it, and the tolerance band gives the allowed deviation. Four-band resistors have two digits; five- and six-band ones have three, for finer values, and the sixth band is the temperature coefficient in parts per million per kelvin. A three-band resistor has no tolerance band, which means ±20%. The calculator checks that each color is valid in its position: gold and silver, for example, are multipliers or tolerances and can never be digit bands.

Worked examples

Four bands, brown-black-red-gold: 10 × 100 = 1 kΩ, ±5%, within 950 Ω to 1.05 kΩ. Five bands, green-blue-black-red-brown: 560 × 100 = 56 kΩ, ±1%, within 55.44 kΩ to 56.56 kΩ. Four bands, orange-orange-brown-silver: 33 × 10 = 330 Ω, ±10%. Six bands, red-red-black-brown-brown-red: 220 × 10 = 2.2 kΩ, ±1%, with a temperature coefficient of 50 ppm/K.

Standard values

Resistors are made in preferred values from the IEC 60063 E series rather than in every number. The E12 series, used with ±10% parts, has the values 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68 and 82 in every decade, and E24, used with ±5% parts, fills in 11, 13, 16, 20, 24, 30, 36, 43, 51, 62, 75 and 91. If your reading gives a value outside the series, such as 5.2 kΩ on a ±5% part, you have most likely misread a band.

Common mistakes

Reading from the wrong end is the first: the tolerance band is usually gold or silver and is set slightly apart, and gold or silver are never the first band. Confusing similar colors is the second, especially brown, red and orange in poor light, so confirm with a multimeter. Third, measuring a resistor while it is soldered into a circuit gives a lower reading because other components are in parallel with it. Finally, the color code does not show the power rating, which depends on the size of the part.

Sources: IEC 60062:2016 (marking codes for resistors and capacitors) for the color assignments and tolerances; IEC 60063 for the E series of preferred values. Related: Ohm’s law calculator, series and parallel calculator, LED resistor calculator and voltage divider calculator.