Reading Resistors
Resistors are too small for printed numbers, so they wear their value as colored bands. Learn the code once and you'll read them at a glance.
The code
| Color | Digit | Multiplier |
|---|---|---|
| Black | 0 | ×1 |
| Brown | 1 | ×10 |
| Red | 2 | ×100 |
| Orange | 3 | ×1,000 |
| Yellow | 4 | ×10,000 |
| Green | 5 | ×100,000 |
| Blue | 6 | ×1,000,000 |
| Violet | 7 | — |
| Gray | 8 | — |
| White | 9 | — |
| Gold | — | ×0.1 (±5%) |
| Silver | — | ×0.01 (±10%) |
How to read: first two bands are digits, third is the multiplier. (The gold/silver band at the end is tolerance — how far off it may be — and goes on the right.)
Worked examples (all verified)
- Red, red, brown → 2, 2, ×10 → 220Ω
- Brown, black, red → 1, 0, ×100 → 1,000Ω = 1kΩ
- Yellow, violet, brown → 4, 7, ×10 → 470Ω
- Orange, orange, red → 3, 3, ×100 → 3,300Ω = 3.3kΩ
- Brown, black, orange → 1, 0, ×1,000 → 10,000Ω = 10kΩ
Check: red-red-brown is the LED resistor from The LED Circuit — 220Ω. If your kit's "220Ω" reads brown-black-red, that's 1kΩ, not 220Ω — close enough to dim an LED noticeably, wrong enough to matter.
The mnemonics (pick one)
"Big Brown Rabbits Often Yield Great Big Vocal Groans When Gingerly Slapped" — Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White, Gold, Silver. Silly is the point; silly sticks.
When bands lie to your eyes
Red vs. orange vs. brown under warm lighting is genuinely hard. The multimeter settles it — measure the resistor (see The Multimeter). Beginners should verify-by-meter whenever the circuit misbehaves; even experienced builders do when the lighting is bad.
E12 values: resistors come in standard values (10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 per decade) — that's why it's always 220Ω and never 200Ω. If your calculation says 187Ω, you buy 180Ω or 220Ω and re-check the math.
Next: The LED Circuit