Free NEC & CEC Electrical Calculators

WirePhase gives electricians, contractors, engineers and trade students 16 fast calculators for wire sizing, voltage drop, conduit and box fill, motors, transformers, solar and EV circuits. Every tool shows its formula and the code reference behind it.

Start here: Voltage Drop Calculator

Read the full voltage drop guide →

All calculators

Load & Power

Ohm's Law & Power CalculatorSolve for voltage, current, resistance or power by entering any two known values. It is handy for…Single-Phase & Three-Phase Power CalculatorConvert voltage and current into kW, kVA and kVAR for single-phase and three-phase systems, with power…Generator Sizing CalculatorEstimate generator capacity from running loads, the starting surge of your largest motor, and a safety…Energy Consumption & Cost CalculatorTurn a load's wattage and daily run time into kWh and dollars per day, month and year using your…

NEC / CEC Code

Voltage Drop CalculatorCalculate voltage drop in volts and percent for copper or aluminum conductors on 120 to 480 V circuits,…Wire Size & Ampacity CalculatorFind the minimum copper or aluminum conductor for a load after ambient temperature and conductor…Conduit Fill CalculatorCheck whether a group of conductors fits in EMT, PVC Schedule 40/80, RMC, IMC or flexible conduit within…Box Fill CalculatorAdd up the required volume for conductors, devices, clamps and grounds, and compare it with the capacity…Derating Factor & Ambient Temperature Correction CalculatorCombine the ambient temperature correction and the conductor-count adjustment into one multiplier and…

Motor & Transformer

Motor Full-Load Current CalculatorLook up full-load current from NEC Tables 430.248 and 430.250, then get the minimum conductor and…Transformer Sizing & Protection CalculatorConvert transformer kVA to primary and secondary current and see the maximum overcurrent protection…Power Factor Correction & Capacitor Sizing CalculatorFind the capacitor kVAR needed to raise power factor from an existing value to a target, with the…Short-CircuitEstimate available fault current at a transformer secondary and at a panel after accounting for wire…

Solar, EV & Green

EV Charger Circuit & Panel Capacity CalculatorFind the breaker, copper wire size for an EV charger; it does not establish service capacity, using the NEC…Solar PV Array & Battery Bank Sizing CalculatorEstimate array wattage, battery energy needs; controller compatibility requires manufacturer checks from your daily energy use, sun…LED & Low-Voltage Drop CalculatorCalculate voltage drop for 12 V and 24 V LED strips and find the longest run before dimming…

Electrical guides

How WirePhase works

Each calculator uses published National Electrical Code (NEC) values, such as Table 310.16 ampacities, Chapter 9 conductor and conduit dimensions, and Tables 430.248 and 430.250 for motors, with the Canadian Electrical Code (CEC) noted where it differs. Formulas, assumptions and worked examples are shown on each page so you can verify results by hand.

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