How it works
Resistor values are encoded as colored bands printed on the body. Each color maps to a digit (0–9), a multiplier, a tolerance, or a temperature coefficient. Reading direction is from the band closest to one end of the body toward the other.
4-band resistors
| Band | Role |
|---|---|
| 1 | First significant digit |
| 2 | Second significant digit |
| 3 | Multiplier (×10^n) |
| 4 | Tolerance |
Example: Yellow–Violet–Red–Gold → 4, 7, ×100 = 4700 Ω ±5%
5-band resistors
| Band | Role |
|---|---|
| 1 | First significant digit |
| 2 | Second significant digit |
| 3 | Third significant digit |
| 4 | Multiplier |
| 5 | Tolerance |
5-band coding is used for 1% (E96) and 0.1% precision resistors where three significant digits are needed. Example: Red–Red–Black–Brown–Brown → 2, 2, 0, ×10 = 2200 Ω ±1%
6-band resistors
A sixth band adds a temperature coefficient (tempco) in ppm/°C:
| Colour | Tempco (ppm/°C) |
|---|---|
| Brown | 100 |
| Red | 50 |
| Orange | 15 |
| Yellow | 25 |
| Blue | 10 |
| Violet | 5 |
6-band resistors appear in precision analog designs, current sensing, and reference circuits where drift with temperature matters.
Color-to-digit mapping
| Colour | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1 k | — |
| Yellow | 4 | ×10 k | — |
| Green | 5 | ×100 k | ±0.5% |
| Blue | 6 | ×1 M | ±0.25% |
| Violet | 7 | ×10 M | ±0.1% |
| Grey | 8 | ×100 M | ±0.05% |
| White | 9 | ×1 G | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Resistor series and tolerance
Standard values follow the E-series, where each series divides a decade into a fixed number of steps:
| Series | Steps/decade | Typical tolerance | Use |
|---|---|---|---|
| E12 | 12 | ±10% | General purpose, legacy designs |
| E24 | 24 | ±5% | Most common for pull-ups, dividers |
| E48 | 48 | ±2% | Precision analog |
| E96 | 96 | ±1% | Precision — current sensing, filters |
| E192 | 192 | ±0.5% / ±0.1% | Metrology, precision references |
For most embedded work — pull-ups, LED current limiters, voltage dividers for ADC scaling — E24 with ±5% is sufficient. Move to E96/1% when tolerances stack: a 3-resistor voltage divider at ±5% each can have over ±9% worst-case error on the output.
Reading direction
If the band spacing is unclear, the tolerance band (gold, silver, brown) is almost always at the right end. On precision 1% resistors (brown tolerance), the gap between band 4 and band 5 is usually slightly wider than the other gaps — that wider gap separates multiplier from tolerance.
When in doubt, measure with a multimeter. Color-code reading is a bench sanity check, not a substitute for measurement in production.
Common mistakes
Reading from the wrong end. Starting from the tolerance band gives nonsense values. The tolerance band (gold, silver) and the tempco band (6-band) are always at the far right end.
Confusing gold/silver as digit vs. tolerance. Gold and silver are only digit values as the multiplier band in a 4-band resistor (meaning ×0.1 or ×0.01 — for sub-10 Ω values). They are never used as the first or second digit.
Ignoring tolerance stacking. Two 10 kΩ ±5% resistors in a voltage divider have a worst-case output error of ±9.75%. If your ADC has a 10-bit range (3.3 V full-scale = 3.2 mV/LSB), a 10% divider error is 330 mV — that’s over 100 LSBs of systematic offset.
Assuming color accuracy on aged resistors. The color coating on carbon film resistors fades and discolors with heat and UV exposure. On anything pulled from a junk box, measure before use.
Using E24 values for precision filter cutoffs. RC filter cutoff frequency depends on R × C. E24 values give only ~10% steps; your nearest standard value may shift fc by 5–10%. For tight cutoffs, select C first from the nearest standard value, then solve for R and pick the nearest E96 value.