Resistor color code calculator
Select the color bands on a resistor to read off its resistance and tolerance.
Fill in the fields and press Calculate to see your result here.
How this calculation works
Each colored band stands for a digit, a multiplier, or a tolerance percentage, following the standard EIA color code. A 4-band resistor uses two digit bands, a multiplier and a tolerance; a 5-band resistor adds a third digit band for finer precision. The digits are read in order and multiplied by the multiplier band's power of ten to give the resistance in ohms.
Worked example
A 4-band resistor reading red–violet–orange–gold: red = 2, violet = 7, so the digits are 27; orange means ×1,000; so 27 × 1,000 = 27,000 Ω (27 kΩ), with gold meaning ±5% tolerance.
Tips
Read the tolerance band first if you're unsure of direction
The tolerance band (commonly gold or silver) is usually set apart from the others with a wider gap, which tells you which end to start reading from.
Confirm with a multimeter
Colours can be hard to read on old or small parts, so measure the resistance to be sure.
Four bands or five
Five-band resistors add an extra digit for finer precision and usually have tighter tolerance.
Standard values
Resistors come in standard series such as E12 and E24, so common results look like 4.7 kΩ or 10 kΩ.
Frequently asked questions
What does the tolerance band mean?
It tells you how far the actual resistance may vary from the labeled value — for example, a 5% tolerance on a 100Ω resistor could measure anywhere from 95Ω to 105Ω.
What's the difference between 4-band and 5-band resistors?
5-band resistors add a third significant-digit band for more precise values (typically tighter tolerances like 1% or 2%), while 4-band resistors are common for more general-purpose, higher-tolerance parts.