Electrician Calculators
Free NEC-based calculators for electricians: voltage drop, wire size, conduit fill and more. Fast, mobile-friendly, with code references.
Free NEC 2023 Electrical Calculators
Each tool runs NEC 2023 code math in your browser — pick a calculator, enter your job specs, and get a plain-English result with the relevant code section.
- 01
Voltage Drop Calculator
Free NEC voltage drop calculator: single- and three-phase, copper or aluminum, AWG and kcmil, parallel sets, 3% branch and 5% feeder checks, wire size tip.
- 02
Wire Size Calculator
Free NEC 2023 wire size calculator: full derating chain — base ampacity, ambient, bundling, 110.14(C) terminal limit, NM-B 60 °C rule, and 240.4(D) breaker cap.
- 03
Wire Ampacity Chart
NEC 310.16 wire ampacity chart: copper and aluminum, 60/75/90 °C columns, the 110.14(C) usable column, 80% continuous values, and reverse amps-to-wire lookup.
- 04
Conduit Fill Calculator
Free NEC conduit fill calculator for EMT, IMC, RMC, and PVC: THHN/XHHW/RHH, Chapter 9 fill limits, the nipple 60% exception, plus minimum conduit size.
- 05
Ohm’s Law & Watts Calculator
Free Ohm’s law and power calculator. Enter any two of volts, amps, ohms, or watts to get the rest — plus the NEC breaker size with 80% continuous-load headroom.
- 06
Box Fill Calculator
Free NEC 314.16 box fill calculator: mixed-AWG conductors, graduated EGC rule, clamps, device yokes, and a standard box library. Instant pass/fail verdict.
- 07
kVA to Amps Calculator
Free bidirectional kVA and amps calculator for single- and three-phase systems. Get transformer full-load current, NEC 450.3(B) breaker size, and 125% ampacity.
- 08
3-Phase Calculator — kW, kVA, Amps
Free 3-phase power calculator: convert volts, amps, and power factor to kW, kVA, and kVAR, or reverse-solve to line amps. NEC 430.22 conductor floor included.
- 09
Generator Size Calculator
Free generator size calculator: add appliances, get required kW with headroom, altitude derating, NEC 445.13 conductor sizing, and NEC 702 transfer-switch rule.
- 10
Residential Load Calculator
Free NEC 2023 residential load calculator: optional (220.82) and standard method side by side. EV charger, HVAC, range demand, and a service-size verdict.
- 11
Conduit Bend Calculator
Free NEC conduit bend calculator for EMT, IMC, RMC: offset, saddle, 90° stub, and back-to-back bends. Get mark distances, shrink, and Chapter 9 radius check.
- 12
Transformer Sizing Calculator
NEC transformer sizing calculator: size kVA from load, then size primary and secondary protection per NEC Table 450.3(B) with automatic column selection.
- 13
Motor FLC & Breaker Calculator
NEC 430 motor calculator: FLC from Tables 430.248/430.250, minimum conductor (430.22), max breaker (Table 430.52), and overload relay (430.32) in one tool.
- 14
Ground Wire Size Calculator
Free NEC 2023 ground wire calculator: EGC (Table 250.122), GEC (Table 250.66), bonding jumpers (250.102), 250.122(B) upsize for long runs. Copper or aluminum.
- 15
Electrical Estimate Calculator
Free electrical estimate calculator for contractors: burdened labor, material markup, overhead, contingency, and target net margin with a break-even floor.