Resistor Calculator
Resistor calculator works out Resistance and Tolerance from Direction, Number of bands and Band 1. The default figures on this page give resistance of 1,000.0000 ohm; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
3 steps
- 4-band code: brown - black - red - gold.
- Significant figures 10, multiplier x100: 10 x 100 = 1000 ohm.
- Tolerance +/-5% gives 950 to 1050 ohm.
Band colourstable
What each band meanstable
Its 5 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
2 sources
What the resistor calculator calculates
Reads a 3, 4, 5 or 6 band resistor colour code into a resistance, tolerance, temperature coefficient and value range, and writes the band colours for a resistance you name.
How to use this resistor calculator
Enter Direction, Number of bands, Band 1 and Band 2. Resistance updates as you type, and “Use a worked example” loads checked figures you can adjust. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Resistance, Tolerance and Minimum value in tolerance.
The method follows IEC 60062, Marking codes for resistors and capacitors and IEC 60063, Preferred number series for resistors and capacitors.
Brown-black-red-gold example
With Number of bands: 4, Band 1: brown, Band 2: black, Band 3: red, the calculator returns Resistance: 1000, Tolerance: 5, Minimum value in tolerance: 950. This example is checked against an independent source in the test suite.
What you can compare
Change one input at a time to see how it affects Resistance, Tolerance and Minimum value in tolerance. The inputs you can vary are Direction, Number of bands, Band 1, Band 2, Band 3 and Band 4.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How do I calculate what resistor I need?
Reads a 3, 4, 5 or 6 band resistor colour code into a resistance, tolerance, temperature coefficient and value range, and writes the band colours for a resistance you name. Open “How this is worked out” beside the result to see each step for your own figures.
How do I convert resistor value to a color code?
It needs Direction, Number of bands, Band 1, Band 2, Band 3 and Band 4. Nothing else is required, and the figures stay in your browser.
How do I calculate the resistance of a resistor?
The result gives Resistance, Tolerance, Minimum value in tolerance, Maximum value in tolerance, Temperature coefficient and Band colours, each labelled with its unit so the figure can be read on its own.
Can you provide me with a resistor calculator for LEDs?
Reads a 3, 4, 5 or 6 band resistor colour code into a resistance, tolerance, temperature coefficient and value range, and writes the band colours for a resistance you name. Put your own figures in above and the working updates beside the result. For scale, the default figures on this page give 1,000.0000 ohm.
What information do I need for the resistor calculator?
You need Direction, Number of bands, Band 1, Band 2, Band 3, Band 4, Band 5 and Band 6. The page opens with default figures that give resistance of 1,000.0000 ohm, so you can see the scale before entering your own.
What does this resistor calculator show?
It shows Resistance, Tolerance, Minimum value in tolerance, Maximum value in tolerance, Temperature coefficient, Band colours, What each band means and Nearest E24 preferred value, with the working and any warnings for your entries.