About Resistora
Resistora helps engineers, students, and makers find the exact resistor combination or voltage divider for a target value — starting from the resistors they actually have on hand. Instead of adding up resistors you've already picked and hoping the total is close enough, Resistora works backwards from the target value you need and searches your parts bin for the combination that gets you there.
The Problem We're Solving
Standard resistor values come in discrete steps — E12, E24, E96, and so on — so an exact match for a given target almost never exists in a small parts bin. As the bin grows, the number of possible series, parallel, and mixed combinations explodes combinatorially, quickly outpacing what anyone can check by hand. Manually searching for the closest buildable combination is slow, tedious, and error-prone. That gap is exactly what Resistora closes.
Who Builds Resistora
Resistora is built and maintained by a small team of electrical engineers and software developers who wanted a resistor calculator that starts from the target value you need rather than the parts you already picked.
Our Approach to Accuracy
Every combination Resistora returns is always buildable from exactly the resistors you supplied, with quantities respected — no substitutions, no phantom parts. That said, you should always double-check tolerance, voltage, and power ratings against your actual components before building anything; see our Terms of Service for our full engineering accuracy disclaimer.
Get in Touch
We'd love to hear from you — feedback, bug reports, and feature requests are all welcome. Reach us at [email protected].