Updated 18 August 2026. Range figures are planning estimates, not guarantees. Weather, rider, route, bike, battery age and assistance level can change the result substantially.
Quick calculator: multiply battery voltage by amp-hours to get watt-hours: V × Ah = Wh. Then divide usable watt-hours by expected energy use per mile. A practical starting band is 12–20Wh per mile for efficient pedal-assist riding and 20–35Wh per mile for hills, heavy loads or high-output use.
E-bike range formula
Estimated range = usable battery watt-hours ÷ watt-hours per mile
For conservative planning, use about 90% of the labelled battery capacity rather than assuming every rated watt-hour will be available:
Estimated range = (volts × amp-hours × 0.9) ÷ Wh per mile
Example: a 48V 15Ah battery contains 720Wh on paper. Using 90% gives 648 usable Wh. At 15Wh per mile, estimated range is about 43 miles. At 25Wh per mile, it falls to about 26 miles.
Battery capacity and estimated range table
| Battery | Rated capacity | Efficient assist (12–20Wh/mi) |
Hills/high output (20–35Wh/mi) |
|---|---|---|---|
| 36V 10Ah | 360Wh | 16–27 miles | 9–16 miles |
| 36V 15Ah | 540Wh | 24–41 miles | 14–24 miles |
| 48V 15Ah | 720Wh | 32–54 miles | 19–32 miles |
| 48V 20Ah | 960Wh | 43–72 miles | 25–43 miles |
| 52V 20Ah | 1,040Wh | 47–78 miles | 27–47 miles |
These bands already apply a 10% usable-capacity allowance. A light rider on flat roads using low assistance may travel farther. Cold weather, soft tyres, repeated stops, steep climbs or throttle-heavy riding may produce less.
How far will a 36V 10Ah e-bike battery go?
A 36V 10Ah battery has 360Wh of rated energy. A sensible planning range is roughly 16–27 miles for efficient pedal-assist riding or 9–16 miles in demanding conditions. This size suits shorter commutes and lighter folding bikes, provided the voltage, current capability, connector, charger and mounting system all match.
How far will a 48V 20Ah battery go?
A 48V 20Ah battery has 960Wh of rated energy. Using the same planning method, expect around 43–72 miles under efficient pedal assist or about 25–43 miles for harder use. Large advertised figures normally assume favourable test conditions, low assistance and a fully healthy battery.
Compare current 36V, 48V, 52V and 72V e-bike battery options. Match by complete system specification rather than choosing voltage and capacity alone.
What changes e-bike range?
Assistance level and throttle use
High assistance draws more energy. Pedalling with the motor can sharply improve range compared with relying on power-on-demand. Any throttle setup used on public roads must also satisfy the applicable UK legal and approval rules; see whether a disabled throttle changes UK legality.
Rider and cargo weight
More mass requires more energy during acceleration and climbing. Cargo bikes, trailers and heavy locks should be included when planning a return journey.
Hills and stop-start riding
Climbing converts battery energy into height. Frequent acceleration also consumes more than steady riding. Regenerative braking is uncommon on most geared hub and mid-drive e-bikes and should not be assumed.
Speed and wind
Air resistance rises rapidly as speed increases. A headwind can turn an easy route into a high-consumption ride even when the distance is unchanged.
Tyres, brakes and drivetrain
Under-inflated tyres, rubbing brakes, dry chains and misaligned wheels waste energy. Fat tyres and aggressive off-road tread normally need more power than efficient road tyres.
Temperature and battery age
Cold conditions reduce available performance, while battery capacity falls gradually with age and use. Plan extra reserve in winter and replace a battery only with an authorised compatible unit.
Volts, amp-hours and watt-hours explained
Voltage (V)
Voltage must match the controller and motor system. A higher-voltage battery is not an automatic upgrade. Installing 48V on a 36V-only system can damage components and create a safety risk.
Amp-hours (Ah)
Amp-hours describe charge capacity at the stated voltage. Comparing Ah alone can be misleading: 20Ah at 36V stores less energy than 20Ah at 52V.
Watt-hours (Wh)
Watt-hours make capacity easier to compare across voltages. A 36V 15Ah battery is 540Wh; a 48V 15Ah battery is 720Wh.
How to choose a battery for a commute
- Measure the full daily distance, including detours.
- Choose a realistic Wh-per-mile band for the rider, hills and assistance level.
- Add at least 20% reserve rather than planning to arrive empty.
- Confirm voltage, maximum current, BMS, connector polarity, mount and dimensions.
- Use the battery manufacturer’s approved charger.
- Confirm that the frame, rack and fasteners can safely carry the battery.
For voltage selection and compatibility, read the 36V vs 48V vs 52V e-bike battery guide and the Bafang battery compatibility guide.
Battery and charger safety
The Office for Product Safety and Standards advises buyers to obtain e-bikes, batteries and chargers from reputable sellers and to use only genuine authorised replacement batteries and chargers. Incompatible equipment can create an extreme fire risk.
- Never select a charger only because the plug fits.
- Check charging voltage, current, connector and polarity.
- Do not charge a swollen, damaged, unusually hot or wet battery.
- Charge while awake and present, away from escape routes.
- Do not modify the battery pack or bypass its protection system.
Use the official battery safety guidance for e-cycle users and Buy Safe, Be Safe guidance.
Conversion-kit range planning
Conversion-kit range depends on motor power, controller current, wheel size, bike condition and installation quality as well as battery capacity. Higher-power systems can consume energy quickly when used near their limits. Check the battery’s BMS continuous-current rating against the controller and never assume that a larger Ah number guarantees compatibility.
Start with the electric bike conversion kit range, then use the conversion-kit compatibility checklist before ordering. For public-road EAPC use, check the separate 250W continuous-power, 15.5mph cut-off, pedal and throttle rules.
Frequently asked questions
How do I calculate e-bike battery range?
Multiply volts by amp-hours to get watt-hours, allow a reserve for usable capacity, then divide by expected watt-hours per mile. Example: 48V × 15Ah × 0.9 ÷ 15Wh per mile is about 43 miles.
Is a 48V battery always longer range than a 36V battery?
No. Compare total watt-hours, not voltage alone. A 36V 20Ah battery has 720Wh, the same nominal energy as a 48V 15Ah battery.
What is a good Wh-per-mile figure?
About 12–20Wh per mile is a useful planning band for efficient pedal assist. Hills, high assistance, heavy loads, cold weather or high-output systems may use 20–35Wh per mile or more.
Should I fully drain an e-bike battery?
Do not plan routine rides around a completely empty battery. Keep a practical reserve and follow the manufacturer’s charging and storage instructions.
Can I fit a higher-voltage battery for more speed or range?
Only if the complete motor, controller, display, charger and wiring system is designed for that voltage. An unsupported voltage change can damage components, create a fire risk and affect road legality.
Sources
- OPSS: Battery safety for e-cycle users
- Statutory guidelines on lithium-ion battery safety for e-bikes
- GOV.UK: Buy Safe, Be Safe
Safety guidance checked on 18 August 2026. Range estimates are transparent planning calculations, not manufacturer promises.