Resistor Color Code Calculator
Decode resistor color bands into resistance values. Supports 3, 4, 5, and 6-band axial-lead resistors with live band selection, tolerance, and temperature coefficient.
How to Use
- Pick the number of bands your resistor has (4-band is most common).
- Click each band to cycle through colors, or pick directly from the color picker below.
- The resistance and tolerance update live on the resistor preview.
- Use the reverse mode to find the bands for a specific resistance value.
- Look for the gold/silver tolerance band — it's always on the right when reading.
Show Work
Color Chart
| Color | Digit | Multiplier | Tolerance | TCR (ppm/°C) |
|---|
Formulas
History of the Color Code
Resistor color banding emerged in the 1920s when the Radio Manufacturers Association (RMA, later EIA) needed a way to mark values on the tiny carbon-composition resistors populating early radios. Printed digits were unreadable at that size; colored bands remained legible even when soldering flux, heat discoloration, or dust obscured the body. The standard was first codified as EIA-RS-279 and has remained essentially unchanged for nearly a century.
The color-to-digit assignment (black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, gray=8, white=9) follows the visible light spectrum with black and white at the low and high ends — so the sequence is partially mnemonic once you see it. Generations of technicians have memorized it with the somewhat dated phrase "Bad Boys Race Our Young Girls But Violet Generally Wins" or the more modern "Better Be Right Or Your Great Big Venture Goes West".
Different band counts correspond to different precision classes: 3-band (tolerance assumed ±20%, now obsolete), 4-band (two digits + multiplier + tolerance, the workhorse for ±5% and ±10%), 5-band (three significant digits for 1% precision), 6-band (adds a temperature coefficient band for precision analog work). Surface-mount resistors switched to printed numeric codes in the 1980s because they're too small for bands to be resolved at typical viewing distances.
About This Calculator
Pick 3, 4, 5, or 6 bands, select the color of each band from the dropdowns, and this tool decodes the resistance value, tolerance, and (for 6-band) the temperature coefficient. Encode mode goes the other way: type a resistance and get the band sequence that represents it.
Orientation tip for the real world: the tolerance band is always on the right when reading. It's often slightly spaced away from the other bands; gold and silver (tolerance-only colors) never appear in the digit positions, so if you see them, that's your right-hand end. Everything runs client-side; no values are transmitted.
Frequently Asked Questions
Which end do I read from?
Start from the end with a band closest to the lead (the "significant" bands are grouped tighter together, while the tolerance band is slightly separated on the other end). The tolerance band is usually gold or silver. If in doubt, the first band is never gold or silver.
What's the difference between 4, 5, and 6 bands?
4-band: 2 digit bands + 1 multiplier + 1 tolerance (most common, ±5% or ±10%). 5-band: 3 digit bands + 1 multiplier + 1 tolerance (precision ±1% or ±2%). 6-band: 5-band + temperature coefficient (TCR) for precision/military work.
What does the tolerance band mean?
Tolerance is the allowed deviation from nominal. A 1kΩ ±5% resistor can actually measure anywhere from 950Ω to 1050Ω. Common tolerances: gold=±5%, silver=±10%, brown=±1%, red=±2%, green=±0.5%, blue=±0.25%.
How do I tell a 4-band from a 5-band resistor?
Count carefully and look for spacing. 5-band precision resistors often have a distinct spacing between the 4th (multiplier) and 5th (tolerance) band. Most consumer resistors are 4-band.
What's the temperature coefficient band (6-band)?
The TCR band indicates how much the resistance changes per degree Celsius (in parts per million). Brown=100 ppm/°C is common; lower values mean more stable resistors for precision circuits.
Why are 4-band resistors most common?
They hit the sweet spot of cost vs. precision for general electronics — ±5% is good enough for most circuits, and manufacturing is cheap. Precision analog, metrology, and medical gear use 5 or 6-band.
Common Use Cases
Identifying a Spilled Bin
Sort through a mixed bin of through-hole resistors by decoding each color code. A must-have bench tool for hobbyists.
Verifying a BOM
Cross-check the color bands on a newly-arrived parts kit against your bill of materials before assembly.
Teaching Electronics
Students learning component identification can test themselves with the interactive band picker.
Field Repair
Reading bands on a damaged circuit board when the component value isn't readable from charring or physical damage.
Designing Custom Assemblies
Picking the right tolerance and TCR for a precision analog front-end or reference circuit.
Buying Vintage/Surplus Parts
Old resistors often lack printed values — only color bands. Decoding them is the only way to identify them.
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