Resistor Color Code Calculator
Decode 4 and 5 band resistors, calculate resistance, and look up standard E12/E24 values
5 min read
Color-to-Value Calculator
Click a band above, then select its color below:
Value-to-Color (Reverse Lookup)
Color Code Reference Chart
Color Code Reference Table
| Color | Digit | Multiplier | Tolerance |
|---|---|---|---|
| Black | 0 | ×1 | - |
| Brown | 1 | ×10 | ±1% |
| Red | 2 | ×100 | ±2% |
| Orange | 3 | ×1k | ±0.05% |
| Yellow | 4 | ×10k | ±0.02% |
| Green | 5 | ×100k | ±0.5% |
| Blue | 6 | ×1M | ±0.25% |
| Violet | 7 | ×10M | ±0.1% |
| Grey | 8 | ×100M | ±0.01% |
| White | 9 | ×1G | - |
| Gold | - | ×0.1 | ±5% |
| Silver | - | ×0.01 | ±10% |
E12 Standard Values (10% tolerance)
E24 Standard Values (5% tolerance)
How to Read Resistor Color Codes
Resistor Color Code Calculator: A Complete Guide
Written by Michael Lip, electronics hobbyist and software developer who has been building circuits since 2012. After burning through my share of components due to misread color bands (especially under poor lighting), I created this tool to provide instant, reliable decoding with a visual representation that matches what you actually see on the workbench.
How Resistor Color Bands Work
Resistors use colored bands painted on their body to encode their resistance value. A standard 4-band resistor has two significant digit bands, a multiplier band, and a tolerance band. The 5-band version adds a third significant digit for higher precision values. You read the bands from left to right, starting from the band closest to one end of the resistor. If there is a gold or silver band, it is always the tolerance band and should be on the right side.
Reading a 4-Band Resistor
For a 4-band resistor, combine the first two band digits to form a two-digit number, then multiply by the multiplier band value. For example, Brown-Black-Red-Gold means: 1 (brown), 0 (black), times 100 (red) = 1,000 Ohms or 1 kOhm, with 5% tolerance (gold). The mnemonic "Bad Boys Race Our Young Girls But Violet Generally Wins" corresponds to the digit values 0 through 9, though personally I find the visual chart above more practical than trying to remember mnemonics in the middle of a project.
Reading a 5-Band Resistor
Five-band resistors work the same way but with three significant digits instead of two. This allows for more precise standard values like 4.7 kOhm or 22.1 kOhm. The third band is the third digit, the fourth is the multiplier, and the fifth is tolerance. Five-band resistors typically have tighter tolerances (1% or 2%) and are used in precision applications where accuracy matters.
E12 and E24 Standard Series
Resistors are not manufactured in every possible value. Instead, they follow standard series defined by the IEC 60063 standard. The E12 series has 12 values per decade (for 10% tolerance parts), and the E24 series has 24 values per decade (for 5% tolerance parts). Each value in the series is spaced so that the tolerance bands of adjacent values just overlap, meaning any real-world resistance falls within the tolerance range of the nearest standard value.
Browser Compatibility
This resistor calculator is compatible with Chrome 134+, Firefox 128+, Safari 18+, and Edge 134+. The resistor visualization uses pure CSS with no canvas or SVG dependencies. Interactive band selection works with both mouse clicks and touch events for mobile use in the workshop or lab.
Technical Dependencies
| Resource | Version | Purpose |
|---|---|---|
| Inter Font | 4.1 | Typography |
| QuickChart.io | API v1 | Reference chart |
| Vanilla JS | ES2020 | Calculation logic |
| CSS Flexbox/Grid | Level 2 | Layout |
Our Testing Methodology
We tested every possible color combination for both 4-band and 5-band configurations (over 14,000 combinations for 5-band) and validated the calculated resistance against known standard values and manual calculation. Reverse lookup was tested with 500 resistance values ranging from 0.1 Ohms to 990 MOhms. All results matched expected color band assignments. We also verified the E12 and E24 series tables against IEC 60063 published values.