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An electric vehicle's range is simply the usable energy in the battery divided by how much energy it uses per kilometre. Battery capacity is quoted in kilowatt-hours (kWh); consumption is quoted in watt-hours per kilometre (Wh/km) or per mile (Wh/mi). Because manufacturers reserve a buffer at the top and bottom of the pack, only a usable percentage (typically 85–95%) actually drives the wheels.
| Quantity | Formula |
|---|---|
| Range (km) | BatterykWh × (Usable%/100) × 1000 / ConsumptionWh/km |
| Battery needed (kWh) | Range × ConsumptionWh/km / (1000 × Usable%/100) |
| Average consumption | Consumption = Usable Wh / Distance |
| Efficiency (km/kWh) | 1000 / ConsumptionWh/km |
Real-world range varies with speed, temperature, terrain, load and driving style — cold weather and highway speeds can raise consumption by 20–40%. Use the actual Wh/km your car reports for the most accurate estimate.
Range equals the usable battery energy divided by the energy consumption per distance: Range(km)=Battery(kWh)×(Usable%/100)×1000/Consumption(Wh/km). More kWh or lower Wh/km gives more range.
Most passenger EVs use roughly 130–200 Wh/km (about 210–320 Wh/mi). Small efficient cars sit near 130–150 Wh/km, while large SUVs and fast highway driving push it toward 200 Wh/km or more.
Manufacturers reserve a buffer at the top and bottom of the pack to protect the cells and extend life, so only 85–95% of the nominal kWh is actually available to drive. Always base range on the usable figure.
Official ratings use gentle standardised cycles. Real driving adds highway speed, cold or hot weather, heating/AC, headwind, hills, extra passengers and cargo — all of which raise Wh/km and cut range, sometimes by 20–40%.
Cold reduces battery capacity and adds cabin heating load, so winter range can drop 20–40%. Preconditioning the car while plugged in and using seat heaters instead of cabin heat helps recover some of it.
Divide 1000 by the Wh/km value. For example, 150 Wh/km equals 1000/150=6.7 km/kWh. This "kilometres per kWh" figure is an easy efficiency comparison, like miles per gallon.
Rearrange the formula: Battery(kWh)=Range×Consumption(Wh/km)/(1000×Usable%/100). For 400 km at 150 Wh/km and 90% usable you need about 67 kWh.
Yes. Aerodynamic drag rises with the square of speed, so highway cruising uses much more energy per km than city driving. Dropping from 120 to 100 km/h can noticeably extend range.
For occasional long trips, yes. For daily use, keeping the charge between about 20% and 80% reduces battery stress and extends its life, at the cost of using less of the total capacity each day.
Extra weight increases rolling resistance and the energy needed to accelerate and climb, so a heavily loaded vehicle uses more Wh/km. The effect is larger in hilly, stop-start driving than on flat highways.
Yes. The formula is identical; just use the smaller battery (often under 2 kWh) and the lower consumption (roughly 10–30 Wh/km) typical of light electric vehicles.
Roughly, yes — doubling usable kWh nearly doubles range if consumption stays the same. In practice a bigger battery adds weight, which slightly raises consumption, so range scales just under linearly.
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