Resistor Calculator

Decode resistor color codes, calculate series and parallel resistance, and find power dissipation. Free, fast, and easy to use.

Calculate

Choose a calculation type, enter your values or select color bands, and click Calculate Now to get instant results with step-by-step solutions.

Complete User Guide

What is a Resistor?

A resistor is an electrical component that limits or controls the flow of electric current in a circuit. Resistance is measured in ohms (Ω) and is usually shown by colored bands on the resistor body. This tool helps you decode those color bands, combine resistors in series or parallel, and calculate power dissipation — all for free.

All Formulas at a Glance

Color Code: R = (digits) × multiplier ± tolerance%

Series: R_total = R1 + R2 + R3 + …

Parallel: 1/R_total = 1/R1 + 1/R2 + 1/R3 + …

Power: P = V² / R  |  I = V / R

4 Calculation Types

Color Code

Decode resistance from 4-band, 5-band, or 6-band color codes on a resistor.

Series Resistance

Calculate total resistance when resistors are connected end to end.

Parallel Resistance

Calculate total resistance when resistors are connected side by side.

Power Dissipation

Find how much power a resistor dissipates using voltage and resistance.

How to Use This Calculator

  1. Pick what you want to calculate — color code, series, parallel, or power.
  2. Enter resistor values or select color bands.
  3. Choose units if needed (ohms, kilohms, megaohms).
  4. Click Calculate Now and see your answer with a step-by-step breakdown and chart.

Resistor Color Code Chart

• Black=0, Brown=1, Red=2, Orange=3, Yellow=4

• Green=5, Blue=6, Violet=7, Gray=8, White=9

• Gold multiplier = ×0.1, Silver multiplier = ×0.01

• Tolerance: Brown ±1%, Red ±2%, Gold ±5%, Silver ±10%

Quick Examples

• Brown-Black-Red-Gold = 10 × 100 = 1000 Ω (1 kΩ) ±5%

• Two 100 Ω resistors in series = 200 Ω

• Two 100 Ω resistors in parallel = 50 Ω

• 12 V across 100 Ω = 1.44 W power dissipation

Important Notes

  • All resistance values must be greater than zero.
  • Color bands are read from left to right — the tolerance band is usually gold or silver.
  • Unit conversions are done automatically — just pick your preferred unit.
  • At least two resistors are needed for series and parallel calculations.

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