Rough-In: Electrician Calcs

Stop scrolling tables. Get the size.

Every free electrical app hands you Table 310.16 and wishes you luck. Rough-In asks what you know — off the nameplate, off the print — and gives you back the sized answer.

ELEVEN NEC CALCULATORS AND SEVEN FIELD TOOLS

• Motor circuit — horsepower, voltage, phase and motor type in. Out comes the conductor, the branch-circuit device sized for the device type you are actually installing, and the maximum overload setting. It keeps table full-load current and nameplate FLA straight, and tells you which one it used where, because 430.32 is about your motor's plate and nothing else.

• Conduit bending — pick your bender. Ideal, Klein, Greenlee, each with the take-up its maker publishes, cited to the document it came from. Stubs, offsets, kicks, rolling offsets and saddles come back as marks measured from the end of the pipe, with the shrink already accounted for. If your bender's maker publishes nothing, the app says so and asks for the number off your tool instead of quietly guessing.

• Conduit fill — count your hots, neutrals and grounds. Get the raceway size, the fill percentage, and how much room is left: "room for 6 more #12 THHN". Or work it the other way: here is my pipe, what fits?

• Wire sizing — amps in, wire size out, with the derating chain and the termination temperature limit applied and explained.

• Voltage drop — size for a target percentage, or check a size you have already pulled. It tells you when voltage drop rather than ampacity is what set the size.

• Box fill — devices, clamps, grounds and pigtails counted by the rules that actually apply, with the allowance ledger shown line by line.

• Pull boxes — from 4 AWG up a box is not sized by counting wires at all. Enter the raceways coming in and where their conductors go, and get the minimum length, width and depth, each with the rule that set it and the rule that came second. Straight pulls, angle pulls, U pulls, splices and multiple rows of entries on a wall.

Plus dwelling load, circuit loading, grounding and bonding, burial depth, and a tool kit: a bend protractor that reads the pipe, Ohm's law and power, temperature, panel phasing, plugs and receptacles, Ethernet colors, and volume and area.

EVERY ANSWER SHOWS ITS WORK

Tap any result for the step-by-step math, each step with the code section it rests on. Every screen echoes the assumptions it used — 75°C terminations, 30°C ambient, THHN — and every one of them is changeable in Settings and visible in the answer. Nothing is hidden behind a default.

A REFERENCE SECTION THAT READS LIKE A PERSON WROTE IT

Original, plain-English explanations of the rules that trip people up, with worked examples, and a button straight into the calculator that does it.

WORKS WHERE YOU WORK

Every calculation runs on your phone. Basements, mechanical rooms, the back of a job trailer — no signal needed, because nothing here is looked up anywhere else. No ads. No analytics. Nothing you type leaves the device.

Rough-In is a one-time purchase, worked against the NEC 2023 edition. Buy it once — there is no subscription and nothing renews. The store is asked quietly when you have service, and losing service never locks you out of the tools.

Built and tested by members of IBEW Local 175

Reference and training tool. Check every answer against the equipment nameplate, the code edition adopted in your jurisdiction, your AHJ, and the manufacturer's installation instructions.