How to use the Resistor Calculator
The resistor calculator reads a 4-band resistor colour code and shows the resistance and tolerance.
Open the Resistor Calculator →
What you need to enter
- Band 1
- Band 2
- Multiplier
- Tolerance
The formula
Value = (first digit × 10 + second digit) × 10^multiplier, with tolerance as the last band.
Worked example
Using the default values in the calculator:
- Band 1: Brown
- Band 2: Black
- Multiplier: Orange
- Tolerance: Gold ±5%
| Resistance | 10 kΩ ±5% |
| Range | 9.5 kΩ – 10.5 kΩ |
| Ohms | 10,000 |
Tips for better results
- Read from the end without the tolerance band.
- Measure with a meter to confirm.
Common mistakes to avoid
- Reading the bands backwards.
- Confusing similar colours.
Please note: Results are estimates for general use. For safety-critical work such as electrical or building projects, check with a qualified professional and local codes. See our Disclaimer.