Hong Life CalculatorsUnderstanding the e-bike range calculator — concept and principle
How far will an e-bike go on one charge? This calculator estimates range from the battery capacity in watt-hours (or volts × amp-hours), the share of the charge you plan to use and your energy use per kilometre. It also shows riding time, energy use per mile, how many days of commuting one charge covers and how many charges you need per 1,000 km.
How it is calculated
Battery energy (Wh) = V × Ah (or entered directly)
Usable energy = battery Wh × share used ÷ 100
Range (km) = usable energy ÷ Wh per km
Riding time = range ÷ average speed
Days per charge = ⌊range ÷ daily distance⌋; charges per 1,000 km = 1,000 ÷ range
- 1 mile = 1.609344 km; Wh per mile = Wh per km × 1.609344.
The principle
A battery stores a fixed amount of energy. Every kilometre costs some of it, mainly to overcome air drag, rolling resistance and hills, minus whatever your legs contribute. Dividing the energy you are willing to use by the energy per kilometre gives distance, exactly like fuel tank size divided by fuel consumption. Air drag grows quickly with speed, so riding faster raises Wh/km sharply. Many riders avoid draining the battery completely, which is why the calculator asks what share you will use.
Worked example
Default inputs: 500 Wh battery, use 90 %, 11 Wh/km, 20 km/h, 15 km per day.
- Usable energy = 500 × 0.90 = 450 Wh; battery energy = 500 Wh.
- Range = 450 ÷ 11 = 40.9 km = 25.4 miles.
- Riding time = 40.9 ÷ 20 = 2.05 h = 2 h 03 min.
- Energy per mile = 11 × 1.609 = 17.7 Wh/mile.
- Days per charge = ⌊40.9 ÷ 15⌋ = 2; charges per 1,000 km = 24.4.
| Energy use (Wh per km) | Estimated range (km) |
|---|---|
| 2.75 | 163.6 |
| 5.5 | 81.8 |
| 8.25 | 54.5 |
| 11 | 40.9 |
| 13.8 | 32.7 |
| 16.5 | 27.3 |
| 22 | 20.5 |
How to read the result
A field study of a city e-bike measured about 11–18 Wh/km on urban routes and 7–12 Wh/km at steady speeds of 15–25 km/h. Hills, headwinds, heavy loads, low tyre pressure and high assist levels push use toward the top of that range or beyond. If your display reports energy used, divide it by the distance ridden to find your own Wh/km. Cold weather and battery ageing also reduce usable energy.
Common mistakes
- Using the battery's amp-hours alone without multiplying by voltage.
- Assuming the range on the box applies at full assist and high speed.
- Planning to empty the battery completely on every ride.
- Forgetting that range shrinks in winter.
Frequently asked questions
How do I find watt-hours from volts and amp-hours?
Multiply them: 36 V × 13.9 Ah ≈ 500 Wh.
What is a typical e-bike energy use?
Commonly around 7–18 Wh/km depending on speed, terrain and assist level.
Why does range drop in winter?
Lithium-ion batteries deliver less energy when cold, and riders often face more wind and use more assist.
Does pedalling harder extend range?
Yes. Your own power reduces the energy the motor must supply.
Sources: Evtimov I., Ivanov R., Staneva G., Kadikyanov G. (2015), "A study on electric bicycle energy efficiency", Transport Problems 10(3): 131–140 · BIPM, SI Brochure, 9th edition (2019); NIST SP 811, Appendix B (unit conversions)