Resistor Color Code Calculator
Decode a resistor’s color bands into its resistance and tolerance, work backward from a value to the band colors, or total a group of resistors in series or parallel. Pick a mode below — the color-code reader supports 4, 5, and 6-band resistors.
How resistor color codes work
Resistors are too small to print numbers on, so their value is marked with colored bands under the IEC 60062 standard. Reading left to right, the first bands give significant digits, the next band is a power-of-ten multiplier, and a spaced band gives tolerance. A four-band resistor has two digit bands; a five-band adds a third digit for precision; a six-band tacks on a temperature-coefficient band. Once you know the value, combining resistors is simple arithmetic: they add in series and combine by reciprocals in parallel.
How it’s calculated
Digit colors map black=0 through white=9. The multiplier band ranges from ×1 (black) up to ×1G (white), plus ×0.1 (gold) and ×0.01 (silver). Resistance = (significant digits) × multiplier. Tolerance colors give ±1% (brown), ±2% (red), ±0.5% (green), ±5% (gold), ±10% (silver), and so on. Series total = R1 + R2 + …; parallel total = 1 ÷ (1/R1 + 1/R2 + …). Reverse mode factors the value into two or three significant figures and the nearest multiplier.
Reverse mode rounds to the nearest codeable digit pattern, since only certain digit-and-multiplier combinations map to real color bands.
Color code chart
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | — |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | — |
| Yellow | 4 | ×10k | — |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | ×100M | ±0.05% |
| White | 9 | ×1G | — |
| Gold | — | ×0.1 | ±5% |
| Silver | — | ×0.01 | ±10% |
Per IEC 60062 electronic color code.
Worked example
A four-band resistor reads brown, black, red, gold. The digits are 1 and 0 (making 10), the red multiplier is ×100, so the value is 10 × 100 = 1,000 Ω = 1 kΩ, and gold means ±5% — a true value between 950 and 1050 Ω. Put three resistors of 100, 220, and 330 Ω in series and you get 650 Ω; the same three in parallel give about 58.6 Ω.
Common mistakes
- Reading the bands from the wrong end — the tolerance band (gold/silver) goes on the right.
- Mixing up 4 and 5-band layouts, which shifts the multiplier position.
- Confusing the gold/silver multiplier bands with the tolerance band of the same color.
- Adding parallel resistors directly instead of using reciprocals.
Where it is used
- Identifying salvaged or unlabeled resistors on the bench.
- Verifying a build matches its schematic.
- Designing series or parallel combinations to hit a target value.
- Teaching electronics and the color-code standard.
Frequently asked questions
How do you read a resistor color code?
On a 4-band resistor, the first two bands are digits, the third is a power-of-ten multiplier, and the fourth is tolerance. For example green-red-blue-gold is 5, 2, ×1,000,000, ±5% = 52 MΩ ±5%. Five-band resistors add a third digit band before the multiplier.
What is the tolerance band?
The tolerance band (often gold or silver) states how far the real resistance may vary from the marked value. Gold is ±5%, silver ±10%, brown ±1%, and red ±2%. A 1 kΩ ±5% resistor can measure anywhere from 950 to 1050 Ω.
How do I total resistors in series and parallel?
In series, add the values: R = R1 + R2 + R3. In parallel, add the reciprocals and invert: R = 1 ÷ (1/R1 + 1/R2 + …). Two equal resistors in parallel give half their value; in series they give double.
What are the extra bands on a 5 or 6-band resistor?
A 5-band resistor has three significant-figure bands plus multiplier and tolerance for tighter precision. A 6-band resistor adds a sixth band for the temperature coefficient (ppm/K), which tells how much the resistance drifts with temperature.
Can I go from a resistance value back to color bands?
Yes. Switch to reverse mode, type a resistance and tolerance, and the calculator returns the standard band colors. Odd values are rounded to the nearest codeable combination since color bands only represent certain digit-and-multiplier patterns.