Electrical
Calculators for electrical work and design.
Cable Tray Fill Calculator
Check NEC 392.22 cable tray fill for multiconductor and single-conductor cables. Get fill %, pass/fail, and the minimum tray width for ladder, ventilated, and solid-bottom trays. Free, no sign-up.
Box Fill Calculator
Calculate NEC 314.16 box fill from conductors, clamps, support fittings, devices, and grounds. Get the required box volume, fill %, pass/fail, and the minimum box size. Free, no sign-up.
Wire Size & Ampacity Calculator
Find the minimum copper or aluminum wire size for a load using NEC Table 310.16, with 310.15 ambient and conductor-count derating and the 110.14(C) terminal limit. Free, no sign-up.
Conduit Fill Calculator
Size conduit per NEC Chapter 9. Add THHN, XHHW, or other conductors and get the minimum trade size and fill % for EMT, IMC, RMC, PVC, ENT, FMC, and LFMC. Free, no sign-up.
Voltage Drop Calculator
Calculate voltage drop % and the minimum copper or aluminum wire size to stay within the NEC 3% / 5% recommendation, single- or three-phase. Free, no sign-up.
Transformer Sizing Calculator
Size a single- or three-phase transformer from load in kVA, kW, or secondary amps. Get the required kVA, the next standard size, primary and secondary full-load amps, and the NEC 450.3(B) primary OCPD. Free, no sign-up.
Motor FLC Calculator
Look up motor full-load current from NEC Table 430.248/430.250, then get the 125% branch-circuit conductor ampacity, the 430.52 maximum protection by device type, and the disconnect rating. Free, no sign-up.
Ground Wire (EGC) Size Calculator
Size the equipment grounding conductor from the breaker or fuse rating using NEC Table 250.122, copper or aluminum, with the 250.122(B) upsize for enlarged conductors. Free, no sign-up.
Solar String Sizing Calculator
Size a PV string per NEC 690.7. Get the maximum and minimum modules per string from module Voc/Vmp, temperature coefficients, your record-low and high design temperatures, and the inverter voltage window. Free, no sign-up.
EV Charger Circuit Calculator
Size a Level 2 EV charger circuit per NEC 625. Get the minimum breaker and copper or aluminum wire from the 125% continuous-load rule, plus charging power in kW and approximate miles added per hour. Free, no sign-up.