Free EV charging calculators and energy converters
Simple, fast calculators for electric-car charging cost, time, efficiency and charger power, plus energy and electrical unit converters. Every page lists its formula, assumptions and sources.
EV charging and cost calculators
EV Charging Cost CalculatorEstimate what it costs to charge an electric car for any distance from your efficiency and electricity price. Shows kWh used, cost per mile and per 100 miles.EV Charging Time CalculatorEstimate how long it takes to charge an electric car from battery size, start and end charge percentage, charger kW and efficiency.Gas vs Electric Cost per Mile CalculatorCompare the fuel cost of a gasoline car and an electric car over any distance, using MPG, gas price, EV efficiency and electricity price.MPGe, kWh per 100 Miles and Miles per kWh ConverterConvert EV efficiency between MPGe, kWh per 100 miles and miles per kWh using the EPA's 33.705 kWh per gallon conversion factor.EV Charger Power and Range-per-Hour CalculatorConvert charger volts and amps to kilowatts and estimate the miles of range added per hour of charging for your EV's efficiency.EV Range CalculatorEstimate how many miles an electric car can drive from its battery capacity, usable charge and efficiency in kWh/100 mi, miles/kWh or MPGe.EV Road Trip Charging Cost CalculatorEstimate the charging cost of an EV trip, splitting energy between home charging and public fast charging at prices you enter.Cost to Charge an EV Battery (X% to Y%)Find what it costs to charge an electric car battery from any starting percentage to any target, using battery size, efficiency and your price per kWh.EV Home Charging Cost per Month and YearEstimate monthly and yearly home charging cost and kWh for an electric car from daily miles, driving days and your electricity rate.Time-of-Use EV Charging Cost CalculatorCompare EV charging cost under time-of-use electricity rates: enter kWh, the share charged off-peak and both rates to see total and blended cost.Per-kWh vs Per-Minute Charging Price CalculatorCompare public EV charging billed per kWh with charging billed per minute. Find the session cost both ways and the break-even per-minute price.kWh to Miles and Miles to kWh ConverterConvert kilowatt-hours to miles of EV driving, or miles to kWh, using your car's efficiency in kWh/100 mi, miles/kWh or MPGe.eGallon Calculator: Gas Price Equivalent of ElectricityTurn your electricity price into a gasoline-equivalent price per gallon using the U.S. DOE eGallon formula, and find the break-even electricity price.
Energy and unit converters
kW to kWh Calculator (and kWh to kW)Convert kilowatts to kilowatt-hours and back. Enter power and time to get energy, or energy and time to get power, with the formula shown.Watts, Volts and Amps CalculatorFind watts, volts or amps from the other two with P = V × I. Includes kW and an EV charger example (240 V × 30 A = 7.2 kW).EV Charger Amps to kW Chart (120 V, 208 V, 240 V)How many kW is a 16, 32, 40 or 48 amp EV charger? Chart of amps to kW at 120 V, 208 V and 240 V, plus a calculator with miles of range per hour.Amp-Hours to kWh Battery CalculatorConvert battery amp-hours (Ah) to watt-hours and kWh using voltage, or find the Ah needed for a given kWh. Example: 12 V 100 Ah = 1.2 kWh.EV Efficiency Converter: kWh/100 km, Wh/mi, mi/kWh, MPGeConvert EV efficiency between kWh/100 km, kWh/100 mi, Wh/mi, Wh/km, mi/kWh, km/kWh, MPGe and Le/100 km using EPA, NRCan and NIST factors.kWh to BTU, Joules and Therms ConverterConvert kWh to BTU, joules, megajoules and therms, and back, using NIST conversion factors. 1 kWh = 3.6 MJ = 3,412.14 Btu.
How we keep it accurate
Each formula is based on published government and standards sources (EPA, FuelEconomy.gov, U.S. Department of Energy, U.S. Department of Transportation, U.S. EIA, NIST and Natural Resources Canada) and is checked with automated test cases. Calculators give estimates and show the assumptions behind them. Read more about PlugMath.