About this Resistor Color Code
Reading resistor color bands is a fundamental skill for electronics hobbyists and engineers. The colored stripes indicate the resistance value and tolerance. This calculator decodes 4-band and 5-band resistors instantly.
Who this calculator is for
- Electronics students, hobbyists, and technicians identifying resistor values from band colors.
- Anyone troubleshooting a circuit board without a printed resistor value.
- Makers checking tolerance ranges before swapping or selecting parts.
When to use it
- Use it to decode a resistor when the printed schematic lists the value but the component only shows color bands.
- Use it when checking whether a resistor is close enough to the target value and tolerance for your circuit.
- Use it before pairing a resistor value with Ohm's Law or voltage-drop calculations.
How to use this calculator
- Select the Number of Bands (4 or 5).
- Select the color for each band from left to right.
- The calculator displays the Resistance in Ohms (Ω) and the Tolerance range.
Key assumptions
- Band colors are interpreted using the standard resistor color-code system.
- Four-band resistors use two significant digits, while five-band resistors use three.
- The displayed resistance is formatted into ohms, kilo-ohms, or mega-ohms for readability.
Accuracy and testing
Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.
How this calculator works
* 4-Band: Digit 1 | Digit 2 | Multiplier | Tolerance
* 5-Band: Digit 1 | Digit 2 | Digit 3 | Multiplier | Tolerance
Example: Red-Red-Brown (4-band) = 2, 2, x10 = 220 Ω.
Inputs explained
Bands 1-3
These represent significant digits (0-9).
Multiplier
The factor by which the significant digits are multiplied (e.g., Red = x100, Gold = x0.1).
Tolerance
The precision of the resistor. Gold is +/- 5%, meaning a 100Ω resistor could actually be anywhere between 95Ω and 105Ω.
Understanding your results
The output standardizes values (e.g., 4700Ω becomes 4.7 kΩ). The Range tells you the minimum and maximum actual resistance guaranteed by the manufacturer.
Example scenarios
1k Resistor
Brown (1), Black (0), Red (x100). 10 * 100 = 1000 Ω = 1 kΩ.
47k Resistor
Yellow (4), Violet (7), Orange (x1k). 47 * 1000 = 47 kΩ.
Key Features
- 4-Band & 5-Band Support
- Formatted Output (kΩ, MΩ)
- Min/Max Range Calculation
Tips & Best Practices
- Hold the resistor with the tolerance band (usually Gold or Silver) on the right to read it correctly.
- 5-band resistors are generally more precise (1% or 2% tolerance) than 4-band ones.
Glossary of Terms
- Ohm (Ω)
- The SI unit of electrical resistance.
- Tolerance
- The limit of how much the actual resistance may vary from its stated value.