Resistor Calculator
Read a resistor's value from its colour bands or find the colours from a value in ohms.
Tip: A mnemonic for the colour order (0–9): Black Brown Red Orange Yellow Green Blue Violet Grey White.
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About this digital tool
The resistor calculator reads a resistor's value from its colour bands or finds the colours that match a value in ohms. Choose the direction, the number of bands (4 or 5) and the colours, and get the value in Ω, kΩ or MΩ with the tolerance.
The first bands give the digits, another band is the multiplier, and the last is the tolerance. For example, brown-black-red-gold means 10 × 100 = 1 kΩ with a ±5% tolerance. In the reverse direction, you enter the value in ohms and the tool gives the colours. It is useful for electronics, labs, Arduino projects and for anyone who needs to identify a resistor without a multimeter.
How to use
- Choose the direction: colours → value, or value → colours
- Choose the number of bands (4 or 5)
- Choose the colours of each band
- See the value in ohms and the tolerance
- See equivalent resistors in series/parallel
Frequently asked questions
How are the colour bands read?
4 bands: Band 1 (digit 1) + Band 2 (digit 2) + Band 3 (multiplier) + Band 4 (tolerance). E.g., Red-Violet-Orange-Gold = 27 × 1000 = 27kΩ ±5%.
What is the difference between 4-band and 5-band resistors?
4-band: 2 digits + multiplier + tolerance (e.g. 47kΩ ±5%). 5-band: 3 digits + multiplier + tolerance (e.g. 475kΩ ±1%) — more precise.
What does tolerance mean?
How far the real value can deviate from the nominal. Gold = ±5%, Silver = ±10%, Brown = ±1%, Red = ±2%. E.g., 100Ω ±5% = a real value between 95–105 Ω.
How do I read a resistor with 4 bands?
The first two bands are the digits, the third is the multiplier and the fourth the tolerance. Brown, black, red and gold give 10 × 100 = 1000 Ω with ±5%.