Resistor Color Code Calculator
Pick the four band colors to read the resistance value, tolerance and min/max range of any 4-band resistor.
Last updated: 2026-09-15
How the calculation works
- Bands 1 and 2 give two significant digits; band 3 multiplies by a power of ten (gold = 0.1, silver = 0.01).
- Band 4 sets tolerance, which defines the guaranteed min/max range.
- Read bands from the end where they cluster nearest — the tolerance band (gold/silver) sits at the far end.
Formula
R = (digit₁ × 10 + digit₂) × multiplier Range = R × (1 ± tolerance)
| Symbol | Meaning | Unit |
|---|---|---|
digit₁₂ | Two significant digits from bands 1-2 | — |
multiplier | Power of ten from band 3 | — |
tol | Tolerance from band 4 | % |
Worked example
Brown-black-red-gold: (1, 0) × 100 = 1,000 Ω = 1 kΩ ±5%, so the part measures 950–1,050 Ω. Yellow-violet-orange-gold: 4.7 kΩ ±5% — the most common through-hole value.
Interpreting the result
The tolerance band tells you how much the real part can differ from its marking — critical when a circuit needs 1% parts. If a resistor measures outside its color-coded range, it's damaged or misread (check the orientation).
Assumptions
- 4-band axial through-hole resistors (EIA color code).
- Reading direction from the clustered end.
Limitations
- 5-band precision and 6-band (with temperature coefficient) resistors need their own charts.
- SMD resistors use numeric codes (e.g. 103 = 10 kΩ) — not covered here.
Frequently asked questions
Which end do I start reading from?
From the end where the bands are closest together. The gold or silver tolerance band always goes last.
What does a gold multiplier band mean?
Multiply by 0.1 — used for sub-1-Ω values like 4.7 Ω (yellow-violet-gold-gold).