Calculate an electric vehicle’s trip efficiency, compare common efficiency units, or estimate range above a chosen battery reserve. The trip mode distinguishes electricity measured at the charger from electricity reported by the battery or dashboard.
How to use this calculator
In Trip efficiency, enter distance and electricity used over the same trip. Choose At the charger / grid if the energy reading already includes charging losses. Choose From the battery / dashboard if it measures battery consumption; the charging-efficiency input then estimates grid electricity needed to supply it. Enter the actual price per kWh to calculate cost.
Convert units changes between mi/kWh, km/kWh, kWh/100 miles, kWh/100 km, Wh/mile, Wh/km, and MPGe. Battery range uses battery-based efficiency, usable capacity, starting charge, and reserve charge.
Use the same energy measurement boundary
A dashboard can report energy removed from the battery, while a charging meter reports energy drawn from the grid. Charging losses mean these readings need not match. Dividing distance by battery energy gives a higher efficiency number than dividing the same distance by a larger grid-energy quantity.
The trip result and its cost calculations use grid energy. If you supply a battery reading, grid energy is estimated by dividing by charging efficiency. For example, 80% efficiency means 25 kWh delivered to the battery requires 31.25 kWh from the grid. When you enter grid energy directly, the charging-efficiency field is ignored to avoid counting losses twice.
The range tab has a different purpose: it needs battery-based efficiency because the energy available for driving is in the battery. Do not directly substitute an EPA label MPGe or another grid-based figure without reconciling that boundary.
Examples
A measured grid-energy trip
A 100-mile trip using 25 kWh from the grid averages 4 mi/kWh. At $0.15/kWh, trip energy cost is $3.75, or $0.0375 per mile. Using the 33.7 convention, this is 134.8 MPGe as an energy-equivalent calculation.
Planning a charge reserve
A usable 60 kWh battery, starting at 80% with a 10% reserve, has 42 kWh available above reserve. At a battery-based 4 mi/kWh, estimated range is 168 miles, or about 270.37 km.
Formula
grid kWh = battery kWh / (charging efficiency / 100)
miles per kWh = miles traveled / grid kWh
kWh per 100 miles = 100 / miles per kWh
available battery kWh = usable capacity × (starting % − reserve %) / 100
range = available battery kWh × battery-based efficiency
Interpreting the result
Higher mi/kWh means less energy per mile; lower kWh/100 km means less energy per kilometer. Unit conversion itself does not change the measurement boundary. These calculations are not certified EPA testing. Temperature, speed, elevation, cabin conditioning, tire condition, battery health, and usable capacity affect actual range.
Costs include only the electricity price you enter. Session fees, parking, demand charges, subscriptions, taxes not included in your tariff, and other vehicle costs are excluded. Currency selection relabels the amounts without exchanging currencies.
Sources and method
EPA: fuel economy and EV range testing
The worked examples use this calculator’s stated assumptions.