EV Efficiency Converter
Instantly convert between all common electric vehicle efficiency units.
What this calculator does
Convert EV efficiency between common units like mi/kWh, kWh/100mi, Wh/mi, MPGe, kWh/100km, Wh/km, and km/kWh. The converter helps you compare vehicle labels, dashboards, and international units using one consistent input value.
Inputs explained
- Input value: The efficiency number you want to convert.
- Input unit: Select the unit that matches your value.
How it works / Method
- Normalize your input to a base unit of kWh per 100 km.
- Convert the base value to every other unit using standard constants.
- Display the converted values with appropriate rounding.
Formula(s) used
1 mile = 1.609344 km
kWh_per_100mi = 100 / (mi_per_kWh)
kWh_per_100km = 100 / (km_per_kWh)
Wh_per_mi = kWh_per_mi * 1000
MPGe = 33.7 * mi_per_kWh
Conversions are purely mathematical and do not change real world efficiency.
Input
Conversions
| mi/kWh (Range per Energy) | - |
| kWh/100mi (Consumption) | - |
| Wh/mi | - |
| MPGe (EPA) | - |
| km/kWh | - |
| kWh/100km | - |
| Wh/km | - |
Step-by-step example
Example input: 3.5 mi/kWh.
- kWh/100mi: 100 / 3.5 = 28.57 kWh/100mi.
- kWh/100km: 100 / (3.5 * 1.609344) = 17.75 kWh/100km.
- Wh/mi: (1 / 3.5) * 1000 = 285.7 Wh/mi.
- Wh/km: 285.7 / 1.609344 = 177.5 Wh/km.
- MPGe: 33.7 * 3.5 = 118.0 MPGe.
Use cases
- Compare EVs listed in different regions and unit systems.
- Translate dashboard efficiency into kWh/100km for trip planning.
- Convert MPGe to energy per distance for cost calculations.
- Standardize data when building EV spreadsheets or reports.
- Match EPA ratings with real world efficiency numbers.
- Switch between Wh/mi and kWh/100mi quickly.
Assumptions & limitations
- Conversions assume the standard mile to kilometer constant.
- MPGe uses the EPA definition of 33.7 kWh per gallon equivalent.
- Rounding can introduce small differences between units.
- This tool does not estimate range or cost by itself.
- Efficiency can vary with driving conditions, even if units match.
- Results are for comparison, not certification.
Disclaimer: Results are estimates for planning only. Always use manufacturer or test data for official reporting.
Frequently Asked Questions
Divide 100 by your miles per kWh number. So 4 miles per kWh becomes 100 ÷ 4 = 25 kWh per 100 miles. Easy. The two units are reciprocals scaled by 100. Going 5 mi/kWh? That's 20 kWh/100 mi. Going 3 mi/kWh? That's 33.3 kWh/100 mi. The lower the kWh per 100 miles, the more efficient the car. I find kWh per 100 miles more useful for cost math because electricity bills are in kWh — multiply that 25 kWh/100 mi figure by your tariff and you instantly know your fuel cost per 100 miles.
Two-step conversion. First, convert Wh per mile to kWh per mile by dividing by 1000. Then convert miles to km — 1 mile equals 1.609 km, so kWh per km = kWh per mile ÷ 1.609. Multiply by 100 to get kWh per 100 km. Quick example: 250 Wh/mile becomes 0.25 kWh/mile, divide by 1.609 = 0.155 kWh/km, times 100 = 15.5 kWh/100 km. Or skip the steps with a single formula: kWh/100km = (Wh/mile × 100) ÷ (1.609 × 1000) = Wh/mile ÷ 16.09. Easier to remember once you've used it a few times.
Because they measure opposite things. Miles per kWh asks 'how far do you go on one unit of energy?' — bigger number is better. kWh per 100 miles asks 'how much energy do you use to cover 100 miles?' — smaller number is better. They're mathematical inverses scaled by 100. A car doing 5 mi/kWh uses just 20 kWh/100 mi. A thirstier car at 2.5 mi/kWh uses 40 kWh/100 mi for the same distance. Same physics, different framing. The first phrasing sounds like fuel economy in MPG; the second feels more like a power bill. Use whichever makes you think faster.
kWh per mile or kWh per 100 miles — hands down. Your electricity bill is denominated in kWh, so any cost calculation has to land in kWh somewhere. If your efficiency is already in kWh per mile, you just multiply by your tariff and you're done. With miles per kWh, you have to divide first, which adds a step and a chance to make an error. I tell customers — for range conversations, use miles per kWh because it's intuitive. For cost conversations, switch to kWh per mile or kWh per 100 miles. Pick the right tool for the job.
Divide 1000 by your km per kWh figure. So if your car does 5 km per kWh, that's 1000 ÷ 5 = 200 Wh per km. Going 7 km per kWh? That's 143 Wh per km. The two units are reciprocals scaled by 1000 because there are 1000 watt-hours in a kilowatt-hour. Wh per km is the engineer's preferred unit because it makes small efficiency differences obvious — 165 Wh/km versus 175 Wh/km is a meaningful gap, while 5.7 vs 6.0 km/kWh feels less dramatic. Same data, different sensitivity. Use Wh/km if you're geeking out on numbers.
Convert both to a common unit — kWh per 100 km is the most universal. US specs often quote kWh per 100 miles or MPGe; Europe uses kWh per 100 km directly. To convert US kWh/100 mi to kWh/100 km, divide by 1.609. So 30 kWh/100 mi = 30 ÷ 1.609 = 18.6 kWh/100 km. For MPGe, first divide MPGe by 33.7 to get miles per kWh, then convert to your preferred unit. Once everything's in kWh/100 km, you can fairly compare a Tesla rated in the US against a VW rated in Europe. Same physics, just different paperwork.
Not at all. Converting units only changes how the same number looks on paper. Whether your car displays 4 mi/kWh, 6.4 km/kWh, 25 kWh/100 mi, or 156 Wh/km, the energy your car actually consumes per kilometer of road is identical. It's the same as converting Celsius to Fahrenheit — the temperature outside doesn't change. Real efficiency is set by the car's design, your driving style, and the conditions. The only way to change real efficiency is to drive differently or change cars. Conversions are just for comparison and understanding, never for actual improvement on the road.
Multiply kWh per 100 miles by your electricity rate per kWh. That's it. So a car using 28 kWh/100 mi at ■8/kWh costs 28 × 8 = ■224 per 100 miles. Or about ■2.24 per mile. To make it more accurate, add 8-10% for charging losses since the grid energy you pay for is higher than what enters the battery. So actual bill cost would be closer to ■245 per 100 miles. This unit is purpose-built for cost math — both sides of the multiplication are in kWh, so no conversions needed. Quick, clean, and easy to explain.
Lower is better, but 'good' depends on the car. A small efficient EV like a Hyundai Ioniq might hit 220-240 Wh/mile in mixed driving. A mid-size sedan like a Tesla Model 3 typically lands 240-280 Wh/mile. Big SUVs and trucks can be 350-450 Wh/mile or worse. Speed, weather, and load shift the number significantly — same car can do 200 Wh/mile on a calm 60 mph drive and 350 Wh/mile in winter at 80 mph. Compare your car against similar vehicles in similar conditions for a fair benchmark, not against an unrelated class of EV.
Divide MPGe by 33.7. The number 33.7 comes from the EPA's standard — they treat 33.7 kWh of electricity as equivalent in energy to one US gallon of gasoline. So a 120 MPGe vehicle gives you 120 ÷ 33.7 ≈ 3.56 miles per kWh. A 100 MPGe car comes out to 2.97 miles per kWh. Once you've got mi/kWh, the rest of the EV math falls into place easily. MPGe was designed to help gasoline car buyers compare EV efficiency in familiar units, but for actual EV ownership math, miles per kWh is more useful.
Sources & references
- U.S. EPA: Fuel economy and EV range testing - Defines MPGe and the 33.7 kWh per gallon equivalent.
- U.S. DOE: MPGe fact of the week - Explains MPGe as an energy equivalence.
- U.S. Energy Information Administration: Measuring electricity - Defines kW and kWh units used in EV efficiency.
- Schema.org: FAQPage, WebPage, and BreadcrumbList - Structured data definitions used on this page.