Electrician Calculators
Five free, offline NEC electrician calculators in one jobsite tool: voltage drop, conduit fill, conduit bending, box fill, and wire ampacity. Each runs the code math live as you type and cites the governing NEC table, so you get a verifiable answer without a signal or a subscription.
Size a run so the load still gets clean voltage. Keeps you under the 3% branch / 5% total recommendation.
NEC 215.2(A) · Ch.9 Tbl 8Wire Ampacity calculatorWhat copper or aluminum can a load ride on? Smallest conductor rated for your amps at the right termination temp.
NEC Table 310.16Conduit Fill calculatorSmallest legal conduit for your wires. 1 wire = 53%, 2 = 31%, 3+ = 40% max fill.
NEC Ch.9 Tbl 1,4,5Box Fill calculatorDoes it all fit? Counts conductors, devices, clamps and grounds against the box volume.
NEC 314.16Conduit Bending calculatorMark your bends right the first time. Offset spacing, shrink, and 90° stub take-up.
Box-offset & 90° stubWhy Fieldwatt
- Free forever — no account required to run any calculator.
- Works fully offline once the app has loaded.
- Cites the governing NEC table or article for every result.
- Fast and mobile-first — live results with no submit button.
All five calculators
- Voltage Drop calculator — NEC 215.2(A) · Ch.9 Tbl 8
- Wire Ampacity calculator — NEC Table 310.16
- Conduit Fill calculator — NEC Ch.9 Tbl 1,4,5
- Box Fill calculator — NEC 314.16
- Conduit Bending calculator — Box-offset & 90° stub
For guidance only. Always verify against the current National Electrical Code and your local amendments. Fieldwatt does not replace an engineer of record.