Convert electric-vehicle efficiency to miles per gallon equivalent, or estimate a trip’s MPGe from electricity and gasoline used over the same distance. MPGe compares energy quantities; it does not say how many gallons an electric car actually consumes.
How to use this calculator
Use Convert MPGe for a known efficiency value, choosing its units explicitly. Use Trip MPGe for measured miles or kilometers plus grid electricity and gasoline. Enter zero gasoline for an electric-only trip, or zero electricity for a gasoline-only trip. At least one energy input must be positive.
Gasoline can be entered in US gallons or liters. Its price must use the same selected unit. If you change gallons to liters, update both quantity and price accordingly. Electricity should be grid or charger energy including charging losses, not a battery-only reading.
The 33.7 kWh gasoline-equivalent convention
The EPA consumer explanation uses 33.7 kWh as the energy equivalent of one US gallon of gasoline. This calculator uses that convention consistently. For an electric-only trip, MPGe is miles per kWh multiplied by 33.7. For a mixed-fuel trip, gasoline energy is added to electricity before dividing distance by total equivalent gallons.
This is a trip-based energy calculation, not an official EPA label rating. Official ratings use standardized tests and, for plug-in vehicles, include charging losses. Averaging a vehicle’s gasoline MPG and electric MPGe arithmetically does not correctly combine their energy consumption. The underlying distance and energy totals are needed.
For mixed-fuel results, the table expresses total fuel-plus-electricity energy in equivalent units. Its kWh figures are not the amount of electricity purchased. The trip cost uses the actual electricity and gasoline quantities instead.
Examples
An electric-only journey
Traveling 100 miles on 33.7 kWh gives 100 MPGe. At $0.20/kWh, the electricity costs $6.74, regardless of the gasoline price.
Combining electricity and gasoline
A 100-mile trip using 33.7 kWh plus 1 US gallon of gasoline consumes two gallon-equivalents of energy, giving 50 MPGe. At $0.20/kWh and $4 per gallon, actual energy cost is $10.74.
Formula
equivalent gallons = grid kWh / 33.7 + gasoline in US gallons
MPGe = miles / equivalent gallons
electric-only MPGe = miles per kWh × 33.7
1 US gallon = 3.785411784 liters
trip cost = electricity × electricity price + gasoline × matching fuel price
Interpreting the result
MPGe compares energy efficiency, not fuel prices, emissions, driving range, or total ownership cost. A higher MPGe result does not by itself establish a lower bill at a particular electricity tariff. Upstream energy production and emissions are outside the formula.
For a mixed-fuel or plug-in-hybrid trip, align the distance and both energy readings, and account for starting and ending battery charge. Energy taken from a battery before the measured charging period can otherwise distort the result. This calculator does not apply an official test-cycle weighting or utility factor. Use the Miles per kWh Calculator to convert battery consumption to an estimated grid basis when needed.
Sources and method
EPA: fuel economy and EV range testing
The worked examples use this calculator’s stated assumptions.