JOBSITEWIREElectrician calculators

Electrician calculators built for the jobsite

Fast, accurate and free. Works on your phone, loads instantly, no signup.

Size a circuit

Wire Size CalculatorSmallest wire for your amps and distance, ampacity-checked. Voltage Drop CalculatorVolts and percent lost over a run, with 3%/5% guideline warnings. EV Charger Circuit CalculatorBreaker + wire size for Level 2 charging, continuous-load rule applied.

Check a fill

Conduit Fill CalculatorFill % and pass/fail for THHN in EMT, PVC Sch 40 and rigid. Box Fill CalculatorVolume allowances vs box size, with pass/fail and spare capacity.

Made for work, not for browsing

Every calculator here is built around how electrical work actually happens: one hand on the phone, the other holding a tape measure, in a basement with one bar of signal. Pages load fast, inputs are big enough for gloves, results update as you type, and once a page is open the math runs entirely on your phone — no connection needed.

Results come with the reasoning: which formula ran, which constraint governed, and what the next size up buys you. Every page also explains the calculation with a worked jobsite example, so an apprentice can learn the why while the journeyman gets the number.

These tools use standard formulas and commonly published industry values. They're reference aids for planning and sanity checks — installations must comply with your locally adopted electrical code and belong in the hands of a licensed electrician.