What is a 4-band resistor?

A 4-band resistor uses two digit bands, one multiplier band and one tolerance band. The first three give the value; the fourth gives the precision (±5%, ±10%, etc.).

What do the colors mean?

Black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, gray=8, white=9. Multiplier is the same color scale as a power of ten.

What about 5-band resistors?

This tool handles 4-band resistors. 5-band types add a third significant digit — coming soon.

How is tolerance shown?

Gold = ±5%, silver = ±10%, no band = ±20%. Brown (±1%) and red (±2%) are common precision values.

Is the calculation done locally?

Yes — entirely in your browser, with no upload of your inputs.

Resistor Color Code Calculator

Decode 4-band resistors from colors — and reverse value → colors.

100% private — no uploads Free & unlimited Read tutorial

See how it works

Watch a quick simulation of this tool in action — no file needed.

How to use Resistor Color Code Calculator

Follow these steps — everything happens instantly in your browser.

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Step 1. Set the four bands (1st digit, 2nd digit, multiplier, tolerance) using the dropdowns.
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Step 2. See the resistance value and tolerance range update instantly.
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Step 3. Switch to reverse mode to convert a value back into band colors.