Resistor colour codes: read them in 10 seconds

Resistors are too small to print numbers on, so they use coloured bands. The first time it looks like a puzzle. After a few tries you read them without thinking.

Tap a band on the resistor below and pick its colour. Or type a value you need and it shows you the bands.

Reading 4 bands

1. Hold the resistor so the gold or silver band is on the right.
2. The first two bands are digits.
3. The third band is the multiplier: how many zeros come after the digits.
4. The last band is the tolerance: how far the real value can be off.

Example: yellow, violet, red, gold. Yellow is 4, violet is 7, red means two zeros. So 4, 7, 00 = 4,700 Ω, which is 4.7 kΩ. Gold means ±5%.

The digit colours

• 0 black
• 1 brown
• 2 red
• 3 orange
• 4 yellow
• 5 green
• 6 blue
• 7 violet
• 8 grey
• 9 white

There are memory tricks for this, but honestly the middle is just the rainbow: red, orange, yellow, green, blue, violet are 2 to 7. Black and brown come before it (0 and 1), grey and white after it (8 and 9). Learn that and you're done.

The multiplier is just zeros

The multiplier colour tells you how many zeros to add. Red is 2 zeros, orange 3, yellow 4, and so on. Two special ones for small values: gold divides by 10 and silver by 100. So red, red, gold is 2.2 Ω.

5 bands

Precision resistors, 1% and better, use three digits instead of two. Brown, black, black, red, brown is 1, 0, 0, then two zeros: 10,000 Ω, so 10 kΩ. Brown at the end means ±1%.

Which end do I start from?

• The tolerance band usually sits a bit apart from the others. Put it on the right.
• Gold and silver are almost never the first band.
• Read it both ways. Usually only one direction gives a normal value, like 220, 470 or 4.7k.
• Still not sure? Measure it with a multimeter. Takes 5 seconds and it's always right.

What tolerance means

±5% on a 4.7 kΩ resistor means the real one is anywhere between about 4.47 kΩ and 4.94 kΩ. The tool above shows that range for whatever you pick.

For an LED resistor or a pull-up, it doesn't matter. For timing circuits or voltage dividers, where the exact value changes the result, pick 1% parts.

Values you'll see all the time

• 220 Ω: red, red, brown
• 330 Ω: orange, orange, brown
• 1 kΩ: brown, black, red
• 4.7 kΩ: yellow, violet, red
• 10 kΩ: brown, black, orange
• 100 kΩ: brown, black, yellow

Need to know which value to use in the first place? The LED resistor calculator picks one for LEDs, and Ohm's law covers the rest.