Resistor Color Code Calculator — Read Any Resistor Band
Free resistor color code calculator. Decode a 4-band resistor by color instantly and find the resistance value and tolerance from any resistor colour code in seconds.
| Band | Color | Meaning |
|---|---|---|
| 1st digit | Brown | 1 |
| 2nd digit | Black | 0 |
| Multiplier | Red | ×100 |
| Tolerance | Gold | ±5% |
Reading the four bands left to right decodes to 1 kΩ ±5%.
- Tolerance±5%
ƒShow your work
- 1Band 1 (brown) = digit 1, Band 2 (black) = digit 0 → two-digit number 10
- 2Band 3 (red) = multiplier ×100
- 3Resistance = 10 × 100 = 1,000 Ω
- 4Band 4 (gold) sets tolerance = ±5% — the actual part can measure anywhere in that ± range and still be in spec.
About the Resistor Color Code Calculator
This calculator decodes a standard 4-band resistor color code into its actual resistance value and tolerance — the same reading you'd get with a multimeter, but from just looking at the colored bands printed on the part.
It's a staple tool for electronics hobbyists, students learning circuit basics, and anyone sorting through a parts bin of unmarked resistors trying to identify what's what without a meter handy. It's also useful the other direction — checking that a resistor you're about to solder in actually matches the value your schematic calls for.
Pick each band's color from the dropdowns in left-to-right reading order and it works out the resistance immediately, along with a breakdown of what each individual band contributes.
How it’s calculated
On a 4-band resistor, the first two bands are significant digits, the third band is a power-of-ten multiplier, and the fourth band indicates tolerance. The two digit bands combine into a two-digit number, which is then multiplied by the third band's multiplier value to get the resistance in ohms.
The tolerance band doesn't change the nominal resistance value — it tells you the manufacturing precision, meaning the actual part could measure anywhere within that percentage of the stated value and still be considered in spec. Gold (±5%) and silver (±10%) are the most common tolerance bands on general-purpose resistors.
Frequently asked questions
Which end of the resistor do I read first?
Read from the end furthest from the tolerance band, which is usually gold or silver and set slightly apart from the other three bands — that gap marks it as the last band, so you read the color code starting from the opposite end.
What's the difference between a 4-band and 5-band resistor?
A 4-band resistor has two significant digit bands, while a 5-band resistor has three, giving it one more digit of precision — 5-band resistors are typically used where tighter tolerances (like ±1%) are needed. This calculator handles the more common 4-band case.
What does the tolerance band actually tell me?
It's the manufacturer's guaranteed accuracy range around the stated resistance — a 100Ω resistor with a gold ±5% band could measure anywhere from 95Ω to 105Ω and still be within spec, which matters for precision circuits but rarely for general-purpose use.
Why do my measured and calculated resistance values not match exactly?
A little difference is expected and normal — it should fall within the tolerance band's stated percentage. If a multimeter reading is far outside that range, the resistor may be damaged, mislabeled, or misread.
Related calculators
Powered by GetCalculator.online