Reverse Resistor Calculator: From Value to Color Bands
Quick Start
- Enter a resistance value, e.g., 100, 4.7k, 2M. Upper/lowercase is accepted.
- Optional: choose preferred precision if the exact value is uncommon.
- Review the closest standard value and its color bands.
- If needed, adjust the input to test neighboring values.
This tool converts a numeric value into the corresponding resistor color bands.
Rounding and Standards
Not every numeric value exists as a manufactured part. When the exact target is not available, the calculator snaps to the nearest standard value and then shows the resulting color bands. This mirrors practical part selection in design work.
Worked Examples
- 1000 → Brown–Black–Red–(Gold): 1 kΩ with typical ±5% tolerance.
- 4.7k → Yellow–Violet–Red–(Gold): 4.7 kΩ with typical ±5% tolerance.
- 22k → Red–Red–Orange–(Gold): 22 kΩ with typical ±5% tolerance.
- 1M → Brown–Black–Green–(Gold): 1 MΩ with typical ±5% tolerance.
Common Mistakes
- Mixing units (k vs M) or omitting the unit for large values.
- Expecting an arbitrary value to have an exact color code.
- Assuming tolerance bands are fixed regardless of precision.
- Using commas or unusual separators that break parsing.
FAQ
What if my value isn’t a standard one? The tool returns the nearest practical value and bands.
Why are there 4-band and 5-band results? Higher precision values are often represented with 5 bands.
How accurate is the closest value? It reflects common series spacing and typical manufacturing options.
Can I include spaces or the Ω symbol? Yes—formats like “4.7k”, “4.7 kΩ” are accepted.
Glossary
- Closest standard value: the manufacturable value nearest to your target.
- Tolerance: allowable deviation from nominal (e.g., ±5%).
- Multiplier: scales the significant digits by a power of ten.
- Significant digits: digits encoded by the first bands.