Electricity Calculator

  • Motor Torque Calculator
    Calculate motor torque (N·m) from power in watts and speed in RPM using T = P / (2π·RPM/60). Free, instant electric & mechanical motor torque tool.
  • Joules to Watts Calculator
    Convert joules to watts instantly. Enter energy in joules and time in seconds to find power in watts using P = E / t. Free physics tool.
  • Watts to Joules Calculator
    Convert watts to joules instantly. Multiply power (W) by time (s) to find energy in joules, kilojoules, and watt-hours. E = P × t.
  • Conduit Fill Calculator (NEC)
    Calculate conduit fill percentage and check it against US NEC limits (53% for 1 wire, 31% for 2, 40% for 3+ wires) using wire and conduit areas.
  • Solar System ROI Calculator
    Calculate the return on investment (ROI), net profit, lifetime savings and payback period of your solar panel system. Free solar ROI calculator.
  • Voltage Drop Wire Gauge Calculator
    Find the right AWG wire gauge by amps, distance, and voltage. Picks the smallest copper or aluminum conductor keeping voltage drop under your limit (US/NEC 3%).
  • Watt-Hours to Amp-Hours Calculator
    Convert watt-hours (Wh) to amp-hours (Ah) instantly. Enter battery energy and voltage to find capacity in Ah and mAh using Ah = Wh / V.
  • Electricity Usage Monthly Cost Calculator
    Estimate the monthly electricity cost of any appliance from its wattage, daily hours of use, days per month, and your rate per kWh.
  • Electricity Cost of Appliance Calculator
    Calculate the electricity cost of any appliance. Enter watts, hours per day, days per month and your price per kWh to get daily, monthly and yearly cost.
  • LED Current Limiting Resistor Calculator
    Calculate the series resistor needed to safely drive an LED. Enter supply voltage, LED forward voltage, and current to get resistance and power rating.
  • Daily Electricity Usage Calculator
    Calculate daily, monthly and yearly electricity usage in kWh and cost from any appliance's wattage, hours of use, and your cost per kWh.
  • AC Power Calculator
    Calculate real (W), reactive (VAR) and apparent (VA) power in single-phase AC circuits from voltage, current and power factor. Free online tool.
  • Ah to Wh Calculator
    Convert battery capacity from amp-hours (Ah) to watt-hours (Wh) using Wh = Ah × V. Fast, free energy converter with kWh output.
  • Coulomb's Law Force Calculator
    Calculate the electrostatic force between two point charges with Coulomb's law: F = k·q₁·q₂/r². Enter charges and distance to get force in newtons.
  • kWh to CO2 Emissions Calculator
    Convert electricity use (kWh) to CO2 emissions in kilograms using your grid emission factor. Free, instant kWh to kg CO2 calculator.
  • Power Station Runtime Calculator
    Estimate how long a portable power station or battery (in watt-hours) will run a device. Enter capacity, load watts and efficiency to get runtime in hours.
  • Low Voltage Wire Voltage Drop Calculator
    Calculate voltage drop in low-voltage wiring for LED, landscape & 12V/24V DC systems. Enter current, wire length and AWG gauge to size your cable.
  • Electricity Carbon Footprint Calculator
    Calculate the CO₂ carbon footprint of your electricity use from kWh and your grid emission factor (kg CO₂/kWh), per period and total.
  • Three-Phase Power Calculator
    Calculate three-phase active, apparent and reactive power from line voltage, line current and power factor using P = √3·V·I·cos φ.
  • VinFast Monthly Charging Budget Calculator
    Estimate your VinFast EV's monthly home-charging cost from miles driven, efficiency (mi/kWh), and your electricity rate. Includes yearly and per-mile costs.
  • VinFast VF3 Charging Cost Calculator
    Estimate the cost to charge a VinFast VF3 EV from your start to target state of charge using battery size, charging efficiency, and your electricity rate.
  • Lighting Watts to Amps Calculator
    Convert lighting watts to amps instantly. Enter total fixture wattage, voltage, and power factor to find the current draw for sizing circuits and breakers.
  • Lighting kWh Usage Calculator
    Calculate the kWh energy used by your lighting and its cost. Enter bulbs, watts, hours per day and days to estimate consumption and electricity bills.
  • Maximum Lights per Circuit Calculator
    Find how many light fixtures you can safely put on a circuit. Enter voltage, breaker amps and watts per fixture to get the max count at the 80% rule.

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