How to use the resistor color code calculator
- Choose Read 4, 5 or 6 bands to find the value of a resistor from its colors, or Find 4, 5 or 6 bands to see the colors for a value.
- When reading, pick the color of each band from the left end, where the bands are closest together. The last bands are the multiplier, the tolerance and, on 6 band parts, the temperature coefficient.
- When finding bands, type the resistance in ohms and pick the tolerance. A 4 band part holds two digits and 5 and 6 band parts hold three.
- Read the value, the tolerance range and the band table. Check an important part with a meter.
Formula
4 band: value = (digit 1 digit 2) x multiplier
5 and 6 band: value = (digit 1 digit 2 digit 3) x multiplier
Range = value x (1 - tolerance) to value x (1 + tolerance)
Digits: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9
The multiplier is a power of ten: black 1, brown 10, red 100, orange 1k, yellow 10k, green 100k, blue 1M, violet 10M, gray 100M and white 1G. Gold is 0.1 and silver is 0.01. Gold and silver also mean 5% and 10% in the tolerance band.
Worked example
A resistor with bands yellow, violet, red, gold is 4, 7 and a multiplier of 100, so 47 x 100 = 4,700 ohms, written 4.7 kohms. Gold means 5%, so the real value lies between 4.465 kohms and 4.935 kohms.
A 5 band resistor brown, black, black, brown, brown is 100 x 10 = 1,000 ohms with a 1% tolerance. A 4 band resistor with red, red, gold, gold is 22 x 0.1 = 2.2 ohms at 5%.
To find the bands for 4,700 ohms at 5%, type 4700 and choose 4 bands. The answer is yellow, violet, red, gold.
Which end to read from
Start from the end with the bands grouped closer together, and the tolerance band is usually set apart on the other end. If a resistor has a gold or silver band, that band is nearly always the tolerance, so hold the gold or silver band on the right. If there is no clear gap, measure the resistor with a multimeter to confirm.
Four, five and six band parts
Four band resistors are the common general purpose type with two digits, a multiplier and a tolerance. Five band parts have a third digit and are used for precision parts with tolerances such as 1% or 0.5%. Six band parts add a temperature coefficient in parts per million per degree, which shows how much the value drifts as it heats up.
Values you cannot make with two digits
A 4 band resistor cannot show a value such as 4,750 ohms, because that needs three digits. The tool tells you to try 5 bands. Standard values come from preferred number series, so exact values outside a series may not be sold. Related electronics tools are the Ohm's law calculator and the voltage divider calculator.
Assumptions and limits
- Band colors follow the standard resistor color code, with temperature coefficients for the colors that have one.
- The tolerance and temperature coefficient are those of the color you choose, not measured values.
- Colors that look alike, such as brown, red and orange on small or aged parts, can be misread.
- The value found for a given resistance assumes it can be made with the digits available on that number of bands.
Frequently asked questions
How do you read a 4 band resistor?
The first two bands are digits, the third is the multiplier and the fourth is the tolerance. Yellow, violet, red, gold is 4, 7 and times 100, so 4,700 ohms at 5%.
What does a gold band mean?
On the end of a resistor it means a 5% tolerance. As a multiplier, in the third band of a 4 band part, it means times 0.1.
How is a 5 band resistor different?
It has three digit bands before the multiplier, so it can show values with three significant digits. Its tolerance is usually tighter, such as 1% or 2%.
What is the temperature coefficient band?
On a 6 band resistor, the last band tells how much the resistance changes with temperature, in parts per million per degree. Brown is 100, red is 50, orange is 15, yellow is 25, blue is 10 and violet is 5.