Resistor Calculator
Decode resistor color bands into resistance value and tolerance, or find the color code for a target resistance.
How to use the Resistor Calculator
- Enter your inputs into the Resistor Calculator above.
- Results update instantly as you type — no submit button needed.
- Adjust any value to see how the result changes in real time.
The resistor color code
Standard 4-band: First digit × 10 + Second digit, multiplied by 10^(third band), with tolerance from 4th band
Black 0, Brown 1, Red 2, Orange 3, Yellow 4, Green 5, Blue 6, Violet 7, Gray 8, White 9. Tolerance: Gold ±5%, Silver ±10%, Brown ±1%, Red ±2%.
Worked example
Color bands red-red-brown-gold: 22 × 10¹ = 220 Ω ±5%. Color bands brown-black-orange-silver: 10 × 10³ = 10,000 Ω = 10 kΩ ±10%.
Frequently asked questions
How many bands can a resistor have?
3 (very basic, no tolerance), 4 (standard), 5 (more precise — three significant digits) or 6 (adds temperature coefficient). Most through-hole resistors are 4 or 5 band.
What is tolerance?
The percentage range the actual resistance can deviate from the labeled value. ±5% means a 100 Ω labeled resistor could measure anywhere from 95 to 105 Ω.
Why use specific resistance values?
Standard E12 series: 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2 (then ×10, ×100, ...). Lets manufacturers cover any resistance within ±10% with just 12 values.