E-bike Range Calculator — Battery Range Estimator

Formula

How this is calculated

An e-bike's range is the usable battery energy divided by the energy consumed per kilometre. That consumption has three main components: rolling resistance (proportional to total weight and tyre friction coefficient), aerodynamic drag (proportional to the square of effective wind speed — so doubling speed roughly quadruples aero drag), and gradient force (mass × g × slope). These forces multiplied by speed give mechanical power at the wheel. The motor and controller are not 100% efficient, so the actual power drawn from the battery is higher; the efficiency varies with assist level and is captured by the assist efficiency factor in this model.

The model uses standard engineering constants: rolling resistance coefficient 0.008 (typical for an e-bike tyre on tarmac), drag area CdA ≈ 0.5 m² for an upright rider, and air density 1.225 kg/m³ at sea level. These are representative estimates — real-world values vary with tyre pressure, clothing, riding position, altitude and road surface. The model is deliberately conservative on battery usability: most battery management systems protect cells by limiting discharge to 80–90% of rated capacity.

For a more accurate personal estimate, measure actual consumption on a known route and compare. The range-versus-speed curve shows how dramatically speed affects range: switching from 30 to 20 km/h can add 30–50% range on flat ground because aero drag drops sharply.