is a simple tool that converts between four-band resistor color codes and their value. The page is written in Javascript, with a little jQuery for DOM manipulation. It also works quite well on phones thanks to the powers of everyone’s favorite responsive CSS framework.

The biggest challenge was parsing the variety of inputs the tool can get. 1K1, 1.1k, and 1100, are all valid inputs for the same resistor value. When you add in extra decimals, zeros, and the optional tolerance portion, the input becomes tricky to sanitize!

Resistor Calc Screenshot

I intend to add a few more features to the page in the future, but for now it’s complete and useful for hobbyists / EE students.