Free Electrical Calculators
Free electrical calculators for wire gauge, voltage drop, breaker sizing, conduit fill, and panel load. NEC-aligned tools for electricians — no signup.
15 free calculators · No account required
Wire Gauge (AWG)
Determine the correct wire gauge based on amperage, circuit length, voltage, and allowable voltage drop.
- AWG gauge recommendation
- Voltage drop calculation
Voltage Drop Calculator
Calculate voltage drop and voltage drop percentage for copper or aluminum electrical circuits.
- Voltage drop calculation
- Voltage drop percentage
Breaker Size Calculator
Determine the correct circuit breaker size using NEC continuous load rules.
- NEC 80% continuous load rule
- Standard breaker size selection
Conduit Fill Calculator
Free conduit fill calculator. Check NEC Chapter 9 compliance by wire gauge, conductor count, and conduit size.
- NEC 40% fill rule
- PASS/FAIL compliance indicator
Generator Sizing Calculator
Calculate the correct generator size based on running watts, surge watts, voltage, and NEC continuous load rules.
- Running & surge watt calculation
- NEC 125% continuous load rule
Load Calculation Tool
Calculate total electrical load and determine the correct service panel size using NEC continuous load rules.
- NEC 125% continuous load rule
- Total wattage and amperage calculation
Motor FLA Calculator
Calculate motor full-load amperage (FLA) based on horsepower, voltage, phase, efficiency, and power factor.
- Single-phase and three-phase support
- Efficiency and power factor adjustments
Lighting Foot-Candle Calculator
Calculate foot-candles based on lumens, fixture count, and area size.
- Foot-candle calculation
- Lumens to FC conversion
Transformer Sizing Calculator
Calculate transformer kVA requirements based on load amps, voltage, phase, and NEC continuous load rules.
- Single-phase & three-phase support
- NEC 125% continuous load rule
Electrical Resistance Calculator
Calculate electrical resistance using voltage/current or resistivity, length, and conductor area.
- Ohm's Law resistance calculation
- Resistivity-based resistance
Solar Panel & Inverter Sizing Estimator
Estimate solar array wattage, number of panels, and inverter size based on energy usage and sun hours.
- Solar array sizing
- Inverter sizing
EV Charger Circuit & Load Calculator
Calculate EV charger load, breaker size, wire gauge, and panel impact using NEC continuous load rules.
- EV charger load calculation
- Breaker sizing
Three Phase Power & Cost Estimator
Estimate three-phase power, energy usage, and cost based on voltage, current, and power factor.
- Three-phase kVA calculation
- Real & reactive power
Box Fill Calculator (NEC 314)
Calculate NEC-compliant box fill volume based on conductor count, devices, clamps, and wire gauge.
- NEC Article 314 compliant
- Conductor volume calculation
Generator Transfer Switch Interlock Planner
Plan generator interlock configurations, breaker sizing, and essential load compatibility using NEC guidelines.
- Generator load calculation
- Interlock breaker sizing
Browse All Categories
Explore calculators across every trade vertical on GoBuildCalcs.