An electric car's range is a simple division — the energy in the battery divided by the energy used per mile — but the numbers you divide are not fixed. How full the battery is, how much you want left when you arrive, the speed you drive and the weather all move the answer. This calculator lets you set each of them and see how far you can really go, so you can plan a trip with a sensible margin instead of trusting the number on the window sticker.
How to use the EV range calculator
- Enter the usable battery capacity in kWh (usable, not gross, if your car lists both).
- Enter your consumption in kWh per 100 miles — from the EPA label or your car's trip computer.
- Set the starting charge and the reserve you want left when you arrive.
- Choose the conditions: mild weather, hot with air conditioning, cold with the heater, or a custom reduction.
- Read the range in miles or kilometres and the energy it takes.
To work out the charging stops, use the EV charging time calculator; to price the energy, the EV charging cost calculator.
EV range formula
Consumption (kWh/mile) = kWh per 100 miles ÷ 100
Miles per kWh = 100 ÷ (kWh per 100 miles)
- Usable capacity is the part of the battery the car lets you use
- Weather reduction comes from AAA's 2019 test: 17% hot with A/C, 41% cold with the heater (average of five EVs)
Worked example: 75 kWh battery, 30 kWh per 100 miles
- Full-battery range: 75 ÷ 0.30 = 250 miles.
- Charge from 80% down to a 10% reserve: 70% × 75 = 52.5 kWh, so 52.5 ÷ 0.30 = 175 miles.
- In 95°F heat with A/C: 250 × (1 − 0.17) = 207.5 miles.
- At 20°F with the heater: 250 × (1 − 0.41) = 147.5 miles.
Range by conditions and charge window
The table uses the same 75 kWh car and the AAA test averages. Each value is calculated with the formula above.
| Condition (AAA test average) | Range reduction | Full battery → empty | 80% → 10% reserve |
|---|---|---|---|
| Mild weather (75°F) | 0% | 250 mi | 175 mi |
| Hot 95°F with A/C | 17% | 208 mi | 145 mi |
| Cold 20°F with heat | 41% | 148 mi | 103 mi |
Planning with a real-world margin
The EPA range on the sticker comes from standardized tests and is a good way to compare cars, not a promise for any one trip. Highway speeds above 70 mph, strong headwinds, a roof box, hills and cold batteries all raise consumption. AAA's 2019 study measured the effect of temperature directly: with the heater on at 20°F, the average range of the five cars tested fell by 41%; at 95°F with air conditioning it fell by 17%. Different models, and newer cars with heat pumps, do better or worse, so treat the percentages as a conservative planning figure and enter your own if you know them.
Routine charging habits also change what you can use. Many owners charge to 80% for daily driving to protect the battery, then to 100% only for trips, and fast chargers slow down above 80%. If you plan to stop at a fast charger, arriving with 10–20% charge is typical, so using a reserve of 10% in the calculator mirrors that. Check how long the stop will take with the charging time calculator.
Finally, remember consumption is not constant: it is lowest in mixed city driving, higher at highway speeds. If you have the car already, use the average on your trip computer for the kind of driving you plan, not the lifetime average. For the cost of the electricity you will use, see the EV charging cost calculator, and to compare with a gasoline car, the EV vs gas calculator.
Sources
Hot- and cold-weather range reductions (17% at 95°F with A/C; 41% at 20°F with heater) are the averages from AAA's 2019 study “Cold Weather Reduces Electric Vehicle Range” (newsroom.aaa.com), which tested five EVs on dynamometers; Tesla has disputed the study's applicability to its cars. The EPA fuel economy label (fueleconomy.gov) lists kWh per 100 miles. The range formula is a division of energy by consumption.
Frequently asked questions
How is EV range calculated?
Range = usable battery energy ÷ consumption. A 75 kWh battery in a car using 30 kWh per 100 miles has 75 ÷ 0.30 = 250 miles of range at 100% charge.
Why is my real range different from the EPA range?
Speed, temperature, terrain, wind, tire pressure and driving style all change consumption. Highway speeds and cold weather lower the range; gentle city driving and mild weather can raise it.
How much range does cold weather cost?
AAA’s 2019 dynamometer study of five EVs found an average range loss of 41% at 20°F with the heater on, and 17% at 95°F with air conditioning. Without climate control the cold loss was smaller, about 10% for most cars tested.
Why keep a reserve?
Arriving with 10% or more gives you a margin for detours, headwinds or a busy charger. Starting below 100% (80% is common for battery health and speed) lowers the range too.
Where do I find consumption?
The EPA fuel economy label shows kWh per 100 miles for each model, and most EVs display recent consumption on the trip screen.