About
The purpose of this site, who runs it, and how the content is put together.
About this site
Circuit Design Calculators is a set of browser-based tools for the calculations that come up repeatedly in hardware and printed circuit board design. It has been online since 2020.
Characteristic impedance, propagation delay, trace resistance and parasitics, LED current-limiting resistors, mil-to-mm conversion — the cases where opening a datasheet is overkill but doing the arithmetic by hand is tedious. Results update as you type, and the derived values you need for part selection (dissipation, required ratings) are shown alongside.
About the author
I hold a master's degree in engineering and have worked in hardware design for over ten years. My work centres on circuit and PCB design: power supplies, timing and impedance control for high-speed digital signals, EMC, and part selection and tolerance analysis for volume production.
This site started as my own collection of the calculations I kept redoing at work. That is why each page goes beyond evaluating a formula and covers how to judge the result — whether you have left the range where the approximation holds, whether the design still works once manufacturing tolerances are included, whether worst-case conditions stay within ratings. These are the points that actually come up in design reviews.
Editorial policy
Every calculator page states the formula it uses. Where an approximation is involved — transmission line impedance, for example — the page says so and gives the range over which it is valid. Pages do not just produce a number; they also cover how to interpret it against standards, manufacturing tolerances and derating.
The guidance is based on IPC and other published standards together with design practice in common industrial use. Typical values are given as general guidance only. Always confirm the actual figures for your parts and stack-up against the datasheet and your fabricator's specification.
If you find an error, please get in touch at the address above. Errors in a formula are verified, corrected, and the page's last-updated date is revised.
These are simplified calculations. Final design verification must be based on datasheets and your board manufacturer's specifications.
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Last updated: 29 August 2026