Electricity Calculator

  • Watts to kWh Calculator
    Convert watts and run time to kilowatt-hours (kWh). Enter device power and hours used to find energy consumption for billing or efficiency checks.
  • Residential Electrical Load Calculator (NEC)
    Estimate a US home's total electrical load (VA) and service size in amps using NEC general-lighting, small-appliance, and fixed-appliance loads.
  • Annual Appliance Running Cost Calculator
    Calculate the yearly electricity cost of any appliance from its wattage, daily usage hours, and your price per kWh. Get annual, monthly, and daily costs.
  • Power and Heat Flow Conversion Calculator
    Convert power and heat-flow-rate units: watt, kilowatt, BTU/h, calories per second, ergs, horsepower variants and more, using exact watt-based factors.
  • Electric Field of a Point Charge Calculator
    Calculate the electric field E of a point charge using E = kQ/r². Enter charge Q in coulombs and distance r in meters to get the field in N/C.
  • Horsepower to Amps Calculator
    Convert horsepower (HP) to amps for DC, single-phase, and three-phase motors. Enter voltage, efficiency, and power factor to get current draw in amps.
  • Kilowatts to Amps Calculator
    Convert kilowatts (kW) to amps for DC, single-phase and three-phase AC circuits. Enter power, voltage and power factor to get current in amperes.
  • Total Harmonic Distortion (THD) Calculator
    Calculate Total Harmonic Distortion (THD) from the fundamental and harmonic amplitudes. Get THD as a percentage and ratio instantly with this free tool.
  • Pi Attenuator Calculator
    Calculate Pi attenuator resistor values (series R1 and two shunt R2) for any attenuation in dB and characteristic impedance. Free RF pad designer.
  • PCB Trace Resistance Calculator
    Calculate PCB copper trace resistance from length, width, copper weight and temperature using R = rho*L/A with temperature correction.
  • Op-Amp Gain Calculator
    Calculate operational amplifier voltage gain for inverting and non-inverting configurations from Rf and Rin, plus gain in decibels (dB).
  • LM317 Resistor Calculator
    Calculate the LM317 adjustable regulator output voltage from R1, R2, reference voltage and adjustment current using Vout = 1.25(1 + R2/R1) + Iadj·R2.
  • Duty Cycle Calculator
    Calculate duty cycle as a percentage from pulse on time and total period. Get off time and signal frequency instantly for any PWM or square wave.
  • Quarter Wave Antenna Length Calculator
    Calculate the ideal quarter-wave antenna length from frequency and velocity factor. Get results in meters, cm and inches instantly.
  • Electric Field Between Plates Calculator
    Calculate the uniform electric field between two parallel plates using E = V/d from the voltage and plate separation. Fast, free physics tool.
  • Magnetic Flux Density Unit Conversion Calculator
    Convert magnetic flux density (magnetic induction B) between Gauss, Tesla, Weber and Maxwell units instantly. Enter one value and see all 12 units.
  • Electrical Resistance Unit Conversion Calculator
    Convert electrical resistance between picoohm, nanoohm, microohm, milliohm, ohm, kiloohm, megaohm, gigaohm, abohm and volt per ampere instantly.
  • Electric Potential of a Point Charge Calculator
    Calculate the electric potential V of a point charge using V = kQ/r. Enter the charge in coulombs and distance in meters to get volts instantly.
  • Joule Heating Calculator
    Calculate Joule heating (resistive heat) with Q = I²Rt. Enter current, resistance and time to find heat in joules, power in watts, and kilocalories.
  • Watts to Heating Time Calculator
    Calculate how long a heater of a given wattage takes to warm water. Enter mass, power, temperatures and efficiency to get heating time and energy.
  • Incandescent vs CFL vs LED Bulb Running Cost Comparison (15-Year)
    Compare 15-year running cost (purchase + electricity) of incandescent, CFL and LED bulbs. Currency-agnostic; enter your local price and electricity rate.
  • Water Heating Energy Calculator
    Calculate the energy needed to heat water using Q = m·c·ΔT. Enter volume, start/end temperature and efficiency to get kWh, kJ and joules.
  • Magnetic Field of a Long Straight Wire Calculator
    Calculate the magnetic field B around a long straight current-carrying wire using B = µ0·I/(2π·r). Enter current and distance to get tesla, µT and gauss.
  • Electric Potential Energy Calculator
    Calculate the electric potential energy between two point charges using U = kQ1Q2/r. Enter charges in coulombs and distance in meters to get joules.

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