What are resistor color codes?
Through-hole resistors use colored bands to indicate their value, tolerance, and (on precision parts) temperature coefficient. It’s a compact printed code that works even after decades on a dusty shelf. The system is standardized under IEC 60062 and used worldwide.
How to use this calculator
Two modes cover both directions of the question:
- Colors → Value — pick 4, 5, or 6 bands, then select each band’s color. The calculator draws the resistor and computes the value, tolerance range, and TCR.
- Value → Colors — enter the resistance value (Ω, kΩ, or MΩ) plus a tolerance, and the calculator shows what the resistor should look like.
Everything updates live — change a band color and the resistor’s rendering and value update immediately, no button click needed.
The color code, at a glance
- Black = 0 · Brown = 1 · Red = 2 · Orange = 3 · Yellow = 4
- Green = 5 · Blue = 6 · Violet = 7 · Grey = 8 · White = 9
The mnemonic “Bad Boys Race Our Young Girls But Violet Generally Wins” is one of the classics for remembering the order — a little dated, but it sticks.
4-band, 5-band, or 6-band?
- 4-band — 2 digits + multiplier + tolerance. Standard for general-purpose 5% and 10% resistors. What you’ll find in most hobbyist kits.
- 5-band — 3 digits + multiplier + tolerance. Standard for 1% and tighter precision parts. What you’ll see in most modern electronics with E96 series values.
- 6-band — 3 digits + multiplier + tolerance + temperature coefficient (TCR). Used on precision measurement resistors, current-sense shunts, and anything where the resistance value must stay stable over temperature.
Multiplier band
The multiplier band tells you the power of 10 to multiply the digits by:
- Silver = ×10⁻² · Gold = ×10⁻¹
- Black = ×10⁰ · Brown = ×10¹ · Red = ×10² · Orange = ×10³ · Yellow = ×10⁴
- Green = ×10⁵ · Blue = ×10⁶ · Violet = ×10⁷ · Grey = ×10⁸ · White = ×10⁹
So a resistor coded Yellow-Violet-Red is 47 × 10² = 4700 Ω = 4.7 kΩ. Add a Gold tolerance band and you have the classic 4-band 4.7 kΩ ±5%.
Tolerance band
Only certain colors are used for tolerance:
- Silver = ±10% · Gold = ±5%
- Brown = ±1% · Red = ±2%
- Green = ±0.5% · Blue = ±0.25% · Violet = ±0.1% · Grey = ±0.05%
The tolerance defines the range of acceptable actual values. A 100 Ω ±5% resistor is guaranteed to measure between 95 and 105 Ω.
Reading direction — which end is first?
A common source of frustration: which end do you read from? Two clues:
- Gap position — the tolerance band usually has a slightly wider gap before it. Reading with that gap on the right puts the digits on the left.
- Impossible values — if you read from one end and get a nonsensical result (e.g. starts with silver or gold in the first position), flip the resistor and read from the other end.
Common values worth memorizing
These few show up so often that pattern recognition speeds up the whole workflow:
- 220 Ω ±5% — Red, Red, Brown, Gold — classic LED current-limiting resistor for 5 V logic
- 1 kΩ ±5% — Brown, Black, Red, Gold — pullup / pulldown workhorse
- 4.7 kΩ ±5% — Yellow, Violet, Red, Gold — I²C pullup standard
- 10 kΩ ±5% — Brown, Black, Orange, Gold — general-purpose pullup, arguably the most used resistor value on Earth
- 100 kΩ ±5% — Brown, Black, Yellow, Gold — high-impedance input dividers
Important limitations
This calculator handles standard IEC 60062 color codes only. It does not support:
- SMD (surface-mount) resistors — those use numeric codes (e.g. “473” = 47 × 10³ = 47 kΩ) or EIA-96 alphanumeric codes
- Precision resistors marked with actual values printed on the body
- Wire-wound / power resistors that may use different marking conventions
- 3-band resistors (rare, no tolerance = ±20% assumed)
If you’re troubleshooting a circuit, always measure with a meter — color codes tell you the nominal value, but a resistor could be out of tolerance or damaged. The measured value is the truth.