Electronics
Resistor Color Code Calculator

Use this tool to determine values for resistors by color-code, or you can do it the old fashioned way - here's how the calculation is done:

Color coding on resistors is simple. Each resistor has a value, and that value is expressed as a number. This number represents the amount of resistence, or Ohms. Each color has a specific number assigned to it: Brown = 1, Red = 2, etc. The first band represents the first half of the number (ex: the first half of "10" is "1"), the second band represents the second half of the number (ex: the second half of "10" is "0"), and the third band represents what you multiply that number by. Example:

Band 1 = Red = 2
Band 2 = Black = 0
Band 3 = Orange = 1000

Now, simply combine the values from bands 1 & 2, multiply the result (20) by band 3 (1000). Result: 20,000 Ohms (more commonly expressed as 20K - the "K" stands for "Kilo-Ohms")

The fourth band represents the tolerance - uinless a specific tolerance is expressly stated in a schematic, you can most likely ignore this band (especially in low voltage electronics).

That's all there is to it. Here's a full description of the number values for each color, separated by bands:

Band 1
Black = 0
Brown = 1
Red = 2
Orange = 3
Yellow = 4
Green = 5
Blue = 6
Purple = 7
Gray = 8
White = 9

Band 2
Black = 0
Brown = 1
Red = 2
Orange = 3
Yellow = 4
Green = 5
Blue = 6
Purple = 7
Gray = 8
White = 9

Band 3
Black = 1
Brown = 10
Red = 100
Orange = 1,000
Yellow = 10,000
Green = 100,000
Blue = 1,000,000
Purple = 10,000,000
Gray = 100,000,000
White = 1,000,000,000

Band 4
Gold = +/- 5%
Silver = +/- 10%
None = +/- 20%