Resistor calculator

Decode 3–6 color bands, combine resistors in series or parallel, or calculate round-wire resistance.

Get started

Choose the band count or circuit arrangement. The tolerance band is often separated from the other bands.
For a conductor, enter its round diameter and length. A material preset fills the editable conductivity.

Example

Input

4 bands: green, red, red, gold

Expected result

5,200 Ω ±5%

Try it

Good to know

The calculation runs in your browser. Use consistent units in fields with no explicit unit.

Calculation method

Read the significant digits, multiplier, tolerance and optional temperature coefficient in order. A 3-band resistor has a nominal 20% tolerance. A uniform round conductor uses R = L/(σA). Check the part’s datasheet for special markings.

R_{\rm series}=\sum_i R_i,\quad R_{\rm parallel}=\left(\sum_i 1/R_i\right)^{-1},\quad R_{\rm wire}=\frac{L}{\sigma\pi(d/2)^2}

R_{\rm band}=D\,10^m,\qquad R_{\min,\max}=R_{\rm band}(1\mp t/100)

Calculation mode

4 bands

First digit
Second digit
Multiplier
Tolerance

3 bands

First digit
Second digit
Multiplier

5 bands

First digit
Second digit
Third digit
Multiplier
Tolerance

6 bands

First digit
Second digit
Third digit
Multiplier
Tolerance
Temperature coefficient

Parallel

Resistances in Ω

Series

Resistances in Ω

Round conductor

Length
Length unit · mm / cm / m / km / in / ft / yd / mi
Diameter
Diameter unit · mm / cm / m / km / in / ft / yd / mi
Material preset · Custom / Copper / Annealed copper / Aluminum / Silver / Gold
Conductivity · S/m