Resistor Color Code Calculator
Pick the color of each band on a 4- or 5-band resistor and instantly read its resistance in ohms plus tolerance — runs 100% in your browser with no upload.
🔒 Calculated in your browser — nothing is uploaded.
What this resistor color code calculator does
Choose whether your resistor has 4 or 5 color bands, then set the color of each band from the dropdowns. The tool instantly converts the bands into a resistance value in ohms — automatically adding a k, M, or G prefix — and shows the tolerance. A live band preview mirrors your selections so you can double-check the color order against the physical part. The classic brown, black, red, gold combination, for example, reads out as 1 kΩ ±5%.
How the color bands are read
Each color maps to a fixed value: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, grey 8, and white 9. On a 4-band resistor the first two bands are significant digits, the third is a power-of-ten multiplier, and the fourth is the tolerance. A 5-band resistor adds a third significant digit before the multiplier. Multipliers extend to gold (×0.1) and silver (×0.01) for small resistances, while tolerance bands range from ±0.05% (grey) up to gold ±5% and silver ±10%. The calculator multiplies the digits by the multiplier and reports the matching tolerance.
Frequently asked questions
How do I know which end to start reading from?
Hold the resistor so the tolerance band — usually gold or silver, and often spaced slightly apart — is on the right. Then read the bands left to right into the calculator. If a value looks wrong, try reversing the order.
Is anything I select uploaded to a server?
No. The whole calculation runs locally in your browser with JavaScript. The band colors you pick are never sent, stored, or logged anywhere.
What is the difference between a 4-band and 5-band resistor?
A 4-band resistor uses two significant digits, a multiplier, and a tolerance band. A 5-band resistor adds a third significant digit before the multiplier, giving higher precision — common on tighter-tolerance parts. Pick the matching mode at the top before setting the colors.