Resistor Color Code Calculator
Calculate Resistor Color Code values for science, physics, chemistry, and engineering problems.
This resistor color code calculator decodes a resistor's resistance value and tolerance from its colored bands, or works in reverse to find the correct color bands for a target resistance value.
Select the colors of each band (or enter a resistance value), and the calculator returns the resistance and tolerance.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| Brown-Black-Red-Gold bands | 1,000 Ω ± 5% | Brown=1, Black=0, Red=×100 multiplier, Gold=±5% tolerance. Resistance = 10 × 100 = 1,000 Ω ± 5%. |
| Yellow-Violet-Orange-Silver bands | 47,000 Ω ± 10% | Yellow=4, Violet=7, Orange=×1,000 multiplier, Silver=±10% tolerance. Resistance = 47 × 1,000 = 47,000 Ω (47 kΩ) ± 10%. |
How to Read Resistor Color Bands
On a standard 4-band resistor, the first two bands represent significant digits, the third band is a multiplier (power of 10), and the fourth band indicates tolerance. Each color corresponds to a specific digit (black=0, brown=1, red=2, and so on), following a standardized international color code.
Why Tolerance Matters
The tolerance band shows how much the actual resistance may vary from its labeled (nominal) value - a common gold tolerance band means ±5%, while silver means ±10%. A resistor labeled 1000 ohms with 5% tolerance could actually measure anywhere from 950 to 1050 ohms and still be within spec.
How to Use the Resistor Color Code Calculator
- Open the Resistor Color Code Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the resistor color code calculator works.
Frequently Asked Questions
How do you read resistor color codes?
The first two bands give significant digits, the third band is a power-of-10 multiplier, and the fourth band shows tolerance - each color maps to a specific digit value according to the standard resistor color code.
What does the gold band on a resistor mean?
As the fourth (tolerance) band, gold typically indicates a ±5% tolerance. As a multiplier band, gold represents a multiplier of 0.1.
How many bands does a resistor have?
Most common resistors have either 4 or 5 bands - a 5-band resistor adds a third significant digit for higher precision before the multiplier and tolerance bands.
How do I use this resistor color code calculator?
Enter the known values, review the units or settings, and the calculator updates the result instantly. The formula and example on this page show how the answer is produced.
What does the Resistor Color Code Calculator calculate?
Calculate Resistor Color Code values for science, physics, chemistry, and engineering problems. It is designed for fast browser-based calculations without sign-up, downloads, or manual spreadsheet setup.
What formula does this resistor color code use?
The formula is: Resistance = (Digit1 Digit2) × 10^(Multiplier Band). The resistor color code standard was established by the Radio Manufacturers Association (a precursor to today's EIA, the Electronic Industries Alliance) in the 1920s, adopting colors printed directly on the resistor body because early electronic components were too small to practically print numeric text on - a constraint that made a compact color-based code a practical necessity, and the same basic system, now standardized internationally as IEC 60062, is still used on resistors manufactured today.
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Last updated: September 27, 2026.