About

In electronics, resistors are ubiquitous components used to limit current, divide voltages, and adjust signal levels. Because they are often too small to print numbers on, manufacturers use a standardized color-coding system defined by IEC 60062. Misinterpreting a Red band for Orange can lead to a 10x error in resistance, potentially destroying sensitive components like LEDs or microcontrollers.

This dual-function tool solves two common lab problems: 1) It decodes the color bands into a precise Ohmic value with tolerance, and 2) It calculates the equivalent resistance of multiple resistors arranged in Series or Parallel circuits. The graphical interface allows you to 'build' the resistor visually, ensuring you are reading the bands in the correct order.

Formulas

Series Circuit: Resistance adds up.

R_total = R₁ + R₂ + ... + R_n

Parallel Circuit: Inverse adds up.

1R_total = 1R₁ + 1R₂ + ...

Reference Data

Color	Digit	Multiplier	Tolerance
Black	0	x1 Ω	-
Brown	1	x10 Ω	±1%
Red	2	x100 Ω	±2%
Orange	3	x1 kΩ	-
Yellow	4	x10 kΩ	-
Green	5	x100 kΩ	±0.5%
Blue	6	x1 MΩ	±0.25%
Violet	7	x10 MΩ	±0.1%
Grey	8	-	±0.05%
White	9	-	-
Gold	-	x0.1 Ω	±5%
Silver	-	x0.01 Ω	±10%

Frequently Asked Questions

Start from the end that has bands closer together. The tolerance band (often Gold or Silver) is typically separated by a larger gap and should be on the right side.

A 4-band resistor uses 2 digits for value and 1 for multiplier (less precise). A 5-band resistor uses 3 digits for value and 1 for multiplier, allowing for higher precision values (e.g., 125 Ohms vs 120 Ohms).

Often you won't have the exact resistor value needed for a repair. By combining standard values (like two 100 Ohm resistors in parallel to make 50 Ohms), you can create the custom resistance required.

Tolerance indicates how much the actual resistance might vary from the marked value. A 100 Ohm resistor with 5% tolerance could physically measure anywhere between 95 and 105 Ohms.