Electricity Calculator

  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • VinFast Charging Cost per Mile Calculator
    Estimate the electricity cost per mile to charge your VinFast EV using your kWh rate and energy use per 100 miles. Includes trip cost.
  • Power Dissipation in a Resistor Calculator
    Calculate the power dissipated by a resistor using P = I²·R or P = V²/R. Enter current and resistance, or voltage and resistance, to get watts instantly.
  • Energy Cost Per Hour Calculator
    Calculate the electricity cost per hour of any appliance from its wattage and your kWh rate. See hourly, daily, monthly and yearly running costs instantly.
  • 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.
  • Motor Power Calculator
    Calculate mechanical motor power from torque and RPM. P = T × 2π·RPM/60, with instant output in watts, kilowatts and horsepower.
  • 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.
  • 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.
  • 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.
  • VinFast VF6 Charging Cost Calculator
    Estimate the cost to charge your VinFast VF6 EV. Enter battery size, electricity price, start and target charge, and efficiency to get the dollar cost.
  • VinFast VF9 Charging Time Calculator
    Estimate how long it takes to charge a VinFast VF9 EV from any start to target percent using your charger power, battery size, and efficiency.

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