A bidirectional resistor color code calculator for the terminal. Part of Rosito Bench — a collection of pure C++17 CLI engineering utilities.
Every electronics workbench has a multimeter and a pile of unmarked resistors. Reading color bands by eye is slow and error-prone. Opening a browser to use an online calculator is slower.
resistor lives in your terminal. It is a single binary with no dependencies, no runtime, and no internet connection required. Build it once and it is always there.
- Converts a resistor value and tolerance to color bands
- Converts color bands to a resistor value and tolerance
- Supports 4-band and 5-band resistors
- Supports engineering notation:
2k2,4R7,1M,470k - Displays color bands with ANSI terminal colors
- Validates input against standard resistor tolerance values
- Shows valid measurement range based on tolerance
- No external dependencies — pure C++17
mkdir build
cd build
cmake ..
make# Convert a value to color bands
resistor -v 1000 -p 5
resistor -v 4.7k -p 1
resistor -v 2k2 -p 5%
resistor -v 4R7 -p 5
# Convert color bands to a value
resistor -c red,brown,black,gold
resistor -c yellow,violet,black,brown,brown| Flag | Description |
|---|---|
-v |
Resistor value in ohms. Supports engineering notation: 1000, 4.7k, 2k2, 4R7, 1M |
-p |
Tolerance in percentage: 5, 1, 0.5, 5% |
-c |
Color bands as comma-separated names: red,brown,black,gold |
-h |
Show help |
Note: -v and -p must be used together. -c cannot be combined with -v or -p.
| Tolerance | Color |
|---|---|
| ±0.05% | Grey |
| ±0.1% | Violet |
| ±0.25% | Blue |
| ±0.5% | Green |
| ±1% | Brown |
| ±2% | Red |
| ±5% | Gold |
| ±10% | Silver |
$ resistor -v 220 -p 5
Your resistor's color code should look like this: rd rd bn gl
$ resistor -c yellow,violet,black,brown,brown
The resistor value is: 47.0KΩ +/- 1.0%
Valid range: 46.5KΩ - 47.5KΩ
If the measured value is outside this range, return the resistors lot.
You've been scammed!resistor is the first tool in Rosito Bench — a growing collection of small, dependency-free C++17 CLI utilities for engineers and makers.
Please read LICENSE.md.
If this tool saved you time, consider buying me a coffee ☕
Created by Alex Rosito — Valley Glen, Los Angeles, California