electronicsClassic tool
Resistor Calculator
Add resistors in series or parallel and decode 4-band resistor color codes on one page.
Use this resistor calculator to find equivalent resistance for series and parallel combinations without redoing the math by hand. It also decodes common 4-band color codes, which helps with breadboard work, repairs, Arduino projects, hobby electronics and quick bench checks.
You can paste multiple resistor values into one field to get the series total, parallel equivalent, average value and a cleaned list of parsed components. That makes it easier to compare combinations before soldering, sort mixed parts or verify a simple circuit idea.
The color code section turns four bands into a nominal resistance and tolerance, so you can confirm real components, review multiplier logic and avoid mixing similar parts during assembly.
Use clear inputs to get a more useful result.
When to use series or parallel
In series, resistances add directly. In parallel, equivalent resistance drops because current has more than one path. That matters in LED circuits, current limiting, voltage dividers, prototypes and repair work.
How the color code works
The first two bands define the significant digits, the third band applies the multiplier and the fourth band shows tolerance. A yellow, violet, red and gold resistor therefore means 4.7 kΩ with a ±5% tolerance.
Common questions
Can I type 4.7k or 2.2M?
Yes. The parser accepts plain ohms plus common suffixes such as k, M and G.
Does this work for SMD resistors?
For simple resistance combinations, yes, as long as you already know the nominal value. The color decoder itself is focused on 4-band through-hole resistors.