Free Electrician Calculators

NEC-based tools to help you on the job and on the exam. No account required.

NEC Box Fill Calculator

Calculate box fill per NEC 314.16 with all 5 counting rules. Conductors, clamps, devices, EGCs — step-by-step volume breakdown.

Check conduit fill per NEC Chapter 9 Tables 1, 4 & 5. Supports EMT, IMC, RMC, PVC with THHN, XHHW-2, THW, and RHH wire types.

Look up ampacity per NEC Table 310.16 with temperature correction and conduit fill adjustment factors applied automatically.