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VoltCalcs

Electrical Calculators

The electrical calculators electricians, inspectors, and DIY builders reach for — motor sizing, wire gauge, voltage drop, and load calcs — all running instantly in your browser.

Think of this page as the electrician's calculator set: the trade math that comes up on a job, gathered in one place. This pillar splits its audience down the middle: licensed electricians and inspectors who need a fast cross-check for a panel-load calc or a feeder ampacity look-up, and owner-builders working through a sub-panel install or RV upgrade who want a sanity check before pulling wire. The math is the same either way. Every formula here is sourced from the National Electrical Code (NEC 2023, with notes on 2020/2017 differences where adoption lags), IEC 60364 for international users, or the fundamental laws — Ohm's, Kirchhoff's, the Faraday balance behind transformer ratings. Each calculator names its source so the result is traceable. Two honest caveats: every output is an estimate, and the authority having jurisdiction (AHJ) makes the final call on permits. Don't pull from a calculator straight to a finished install.

The tools group around three jobs. For motor work — sizing breakers, wire, and starters — the motor full-load amps calculator is the entry point, and locked-rotor amps follows for inrush sizing. For branch-circuit and feeder design, voltage drop and wire distance answer the gauge-and-length question NEC Article 215 leaves to math. For transformer and panel-level sizing, the electrical load calculator and kVA-to-amps cover service entrances and three-phase service drops. The generator sizing calculator and the conversion tools (HP-to-watts, kWh, watts-to-amps) round out the toolkit for backup-power planning and unit math. If the project is solar-tied or battery-backed, start in the battery or solar pillar first — the AC side here picks up after the DC side is sized. One last note for inspectors: ampacity tables here follow NEC 310.16 with terminal-temperature derating (75°C column for most residential service equipment), not the 90°C insulation rating, so the numbers match what an AHJ will accept on plan review.

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Energy & Cost

Kilowatt-Hour (kWh) Calculator

Calculate kilowatt-hours and energy cost for any appliance or device. Enter watts, hours of use, and your electricity rate for instant results.

Electricity Cost Calculator

See the daily, monthly, and annual electricity bill impact of running any device. Plug in wattage, hours, and your utility rate for a full cost breakdown.

Appliance Electricity Cost Calculator

See exactly what each appliance costs to run by day, month, and year. Enter wattage, hours of use, and your rate to rank household energy hogs.

Electricity Bill Estimator

Estimate your full monthly electricity bill by category: HVAC, water heating, fridge, lighting, electronics, cooking, laundry, plus fixed delivery charges.

EV Charging Cost Calculator

Calculate the true cost of charging an electric car at home or on the road. Side-by-side Level 1 vs Level 2 vs DC Fast comparison with cost per mile.

Water Heater Electricity Cost Calculator

Compare tank, tankless, and heat pump water heater operating costs with DOE UEF math. Inputs: gallons/day, set temp, inlet temp, and rate.

Wiring & Circuits

Inverter Cable Size Calculator

Find the right cable gauge for your battery-to-inverter connection. Enter inverter watts, voltage, and distance for safe wire sizing.

Wire Distance Calculator

Calculate voltage drop and recommended wire gauge for any distance. Enter amps, distance, voltage, and target drop percentage.

Voltage Drop Calculator

Calculate voltage drop in any wire run. Enter wire gauge, distance, current, and voltage to check if your wiring meets NEC standards.

Motors & Power

Motor FLA Calculator

Calculate motor full load amps for single-phase and three-phase motors. Enter HP, voltage, efficiency, and power factor for instant FLA results.

Amps Draw Calculator

Calculate current draw in amps from watts and volts for any device. Supports single-phase and three-phase loads with power factor adjustment.

Locked Rotor Amps (LRA) Calculator

Calculate motor locked rotor amps (LRA) for starting current estimation. Enter FLA and multiplier based on NEMA code letter.

HP to Watts Calculator

Convert horsepower to watts and watts to HP instantly. Supports mechanical, electrical, and metric horsepower with precise conversion factors.

Equipment Sizing

Electrical Load Calculator

Calculate your home's electrical load and NEC 220 demand for panel and service sizing. Enter loads and quantities for connected and demand estimates.

Fusing Transformer Calculator

Calculate primary and secondary fuse sizes for power transformers. Enter kVA, primary and secondary voltages, and NEC multipliers.

kVA to Amps Calculator

Convert kVA to amps for single-phase and three-phase systems. Enter kVA, voltage, and power factor for instant current and true power results.

Generator Sizing Calculator

Find the right generator size for your loads. Enter running watts, motor surge, and power factor for an instant recommendation with safety margin.