How to use the resistor color code calculator
How the code works
Each colour stands for a number: black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9. On a 4-band resistor: value = (10 × band1 + band2) × multiplier, where the multiplier is 10 raised to the third band's number (gold = ×0.1, silver = ×0.01). The fourth band gives tolerance: gold ±5%, silver ±10%, none ±20%, and precision colours down to ±0.1%.
How to use it
Hold the resistor with the tolerance band (gold, silver, or the one spaced apart) on the right. Set the four dropdowns to the colours from the left and press Read resistor — the drawing at the top updates to match the part in your hand.
Example
Yellow, violet, red, gold: digits 4 and 7, multiplier red = ×100, so 47 × 100 = 4,700 Ω = 4.7 kΩ, and the gold band means ±5% (anywhere from 4.47 kΩ to 4.94 kΩ). Those are the colours loaded when the page opens.
Frequently asked questions
How do I read a 4-band resistor?
The first two bands are digits, the third is the multiplier (how many zeros, as a power of ten), and the fourth — set slightly apart — is the tolerance. Read from the end nearest the bands' cluster.
What do gold and silver mean as the third band?
As a multiplier, gold means ×0.1 and silver means ×0.01 — that is how values under 10 Ω are marked. As the fourth band they mean tolerance: gold ±5%, silver ±10%.
What if there is no fourth band?
A missing tolerance band means ±20% — common on older and very cheap resistors.
How do I remember the colour order?
The digits run black 0, brown 1, red 2, orange 3, yellow 4, green 5, blue 6, violet 7, gray 8, white 9. Generations of technicians learned it with a mnemonic starting ‘Black Boys Race Our Young Girls…’ — or just bookmark this page.
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