Resistor Calculator
Read the resistance and tolerance of a 4-band or 5-band resistor from its colors, or enter a value in ohms to get a 4-band color code for it, from 0.1 Ω to 990 MΩ.
How to use the Resistor Calculator
- Enter your numbers in the Resistor Calculator above.
- Press the Read Resistance or Find Color Bands button to see the result.
- To try other numbers, change any value and press the button again.
The resistor color code
4-band: (first digit × 10 + second digit) × multiplier, ± the tolerance of band 4. 5-band: (first digit × 100 + second digit × 10 + third digit) × multiplier, ± the tolerance of band 5
Digits: Black 0, Brown 1, Red 2, Orange 3, Yellow 4, Green 5, Blue 6, Violet 7, Gray 8, White 9. Multipliers: Black ×1 up to Violet ×10,000,000, which is 10 to the power of the color's digit, then Gold ×0.1 and Silver ×0.01. Tolerances: Brown ±1%, Red ±2%, Green ±0.5%, Blue ±0.25%, Violet ±0.1%, Gold ±5%, Silver ±10%. These follow the IEC 60062 color code. A value to color code is rounded to two significant digits, because a 4-band code holds two, and gets a gold ±5% band.
Worked example
Red, red, brown, gold reads 22 × 10 = 220 Ω ±5%. Brown, black, orange, silver reads 10 × 1,000 = 10 kΩ ±10%. On a 5-band resistor, brown, black, black, brown, brown reads 100 × 10 = 1 kΩ ±1%. The other way, 4700 gives yellow, violet, red, gold for 4.7 kΩ, and 4750 gives yellow, gray, red, gold for 4.8 kΩ, the nearest two-digit value.
Frequently asked questions
How many bands can a resistor have?
Three, four, five or six. A 3-band code has no tolerance band, a 5-band code has three digits instead of two, and a 6-band code adds a temperature coefficient. This calculator reads 4-band and 5-band codes.
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?
Resistors come in the E series of preferred numbers, set out in IEC 60063. The E12 series has 12 values per decade: 1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8 and 8.2, then the same times 10, 100 and so on. It goes with ±10% tolerance, and almost any value is within 10% of one of them. E24 has 24 values per decade for ±5% parts.