Electricity Calculator

  • Electrical Energy Calculator
    Calculate electrical energy from power and time with E = P·t. Enter watts or kilowatts and seconds, minutes or hours to get joules, Wh and kWh.
  • Appliance Amperage Calculator
    Calculate the amperage (current draw) of any appliance from its wattage and voltage. Use I = P / V to size circuits, fuses, and wiring safely.
  • Speaker Impedance Calculator
    Calculate total speaker impedance for series or parallel wiring. Enter up to 4 speaker impedances in ohms to find the combined load on your amplifier.
  • Inverter Size Calculator
    Calculate the right inverter size in VA from your total load in watts and power factor, with a safety margin for surge headroom and reliable operation.
  • Amp Hours (Ah) Calculator
    Convert watt-hours to amp-hours instantly. Enter battery energy in Wh and voltage to find capacity in Ah and mAh using Ah = Wh / V.
  • EV Cost Per Mile Calculator
    Calculate the energy cost per mile of your electric vehicle from its efficiency (miles/kWh) and your electricity rate. See cost per 100 miles and trip cost.
  • Watts to Amps Calculator (Three Phase)
    Convert watts to amps for three-phase AC circuits. Enter power, line-to-line voltage and power factor to get line current in amperes instantly.
  • Watts, Volts, Amps & Ohms Calculator
    Solve for voltage, current, resistance or power from any two known values using Ohm's Law (V=IR) and the power equations P=VI, P=I²R, P=V²/R.
  • Whole Home Electricity Bill Calculator
    Estimate your whole-home electricity bill by adding up each device's kWh, then applying your per-kWh rate and fixed fee. Works in any currency.
  • Appliance Energy Cost Calculator
    Calculate how much an appliance costs to run per day, month, and year from its wattage, hours of use, days per week, and your electricity rate per kWh.
  • Solar Panel System Size Calculator
    Estimate the solar PV system size (kW) and number of panels you need from your daily energy use, peak sun hours, performance ratio and panel wattage.
  • Solar System Size Calculator
    Estimate the solar PV system size (kW) you need from your monthly kWh use, peak sun hours and a system derate factor. Free, instant solar sizing.
  • Volts, Amps, Watts, Ohms Calculator
    Ohm's law calculator: enter any two of voltage, current, resistance or power and instantly compute the other two using V=IR, P=VI, P=I²R, P=V²/R.
  • Monthly Electricity Bill Estimator
    Estimate your monthly electricity bill from kWh usage, your rate per kWh, and any fixed service charge. See monthly and annual cost instantly.
  • VinFast Home Charger Electricity Cost Calculator
    Estimate the monthly and annual electricity cost of charging your VinFast EV at home based on miles driven, efficiency, and your kWh rate.
  • 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 Factor Correction Calculator
    Calculate the kVAR capacitor bank and capacitance (µF) needed to correct power factor from a current to target value at any voltage and frequency.
  • LED Series-Parallel Array Calculator
    Calculate the series resistor, voltage drops, current and power for an LED array with multiple parallel strings of LEDs in series.
  • Watts to Lumens Calculator
    Convert watts to lumens using luminous efficacy (lm/W). Compare LED, CFL and incandescent brightness instantly with this free calculator.
  • Motor Full Load Current Calculator
    Calculate the full load amperes (FLA) of single- and three-phase electric motors from horsepower, voltage, efficiency, and power factor.
  • Three-Phase Current Calculator
    Calculate three-phase line current in amps from power, line voltage and power factor using I = P / (√3 × V × PF). Free and instant.
  • RC / RL Time Constant Calculator (τ)
    Calculate the time constant τ for RC and RL circuits. RC: τ = R·C, RL: τ = L/R. Get τ in seconds, ms, µs and the 5τ settling time.
  • Capacitor Discharge Calculator (RC)
    Calculate the voltage across a discharging capacitor in an RC circuit using V(t)=V₀·e^(−t/RC). Find time constant, percent remaining and current.
  • Amps to Volts Calculator
    Convert amps to volts using power (V = P/I) or resistance (V = I×R). Free online amps to volts calculator with worked examples and formulas.

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