Resistor Color Code Calculator
Decode 4- or 5-band resistors instantly. Select each color band to read the resistance and tolerance range.
Resistance
1 kΩ
Tolerance: ±2% — range: 980 Ω to 1.02 kΩ
Formula
value = (digits) × multiplier ± tolerance
Each colour band maps to a digit, a power-of-ten multiplier, or a tolerance percentage.
How resistor colour codes work
Through-hole resistors are too small to print numbers on, so their value is encoded as a series of coloured rings. Reading from the end with bands grouped closest together: the first bands are significant digits, the next band is the multiplier (how many zeros to add), and the final, slightly separated band is the tolerance.
A 4-band resistor uses two digit bands; a 5-band (precision) resistor uses three. The picture above fills in live as you pick each colour so you can match it against the part in your hand.
Reading tips
- Hold the resistor so the tolerance band (usually gold or silver) is on the right.
- Gold = ±5%, silver = ±10%, brown = ±1%, red = ±2%. No tolerance band means ±20%.
- If both ends look similar, the wider gap before the last band tells you which way to read.
- Use the tolerance range to check a measured value — a 1 kΩ ±5% part can legitimately read 950–1050 Ω.
Where it's used
Every breadboard build, Arduino shield and PCB uses resistors for current limiting, pull-ups/downs, voltage dividers and biasing. Decoding the bands quickly saves time when sorting a mixed bag of components.