Quick answer: Electric bike range is the usable energy in your battery divided by the energy you use per mile. The second number keeps moving: assist level, rider and luggage weight, wind, uphill stretches, cold and tyre pressure all change it. Measure your own rate on a known loop, then plan rides with charge to spare.
What decides an e-bike's range?
Range comes down to one division: the energy your battery can give, divided by the energy you use for each mile. The battery figure hardly changes from ride to ride. The second figure changes all the time, which is why two riders on the same bike can report very different distances. Before you compare packs, our checklist for choosing an adult e-bike puts range next to fit, motor type and charging.
A maker's range figure is a result under the maker's own conditions. Your roads, weight and weather are different, so the figure worth planning with is the one you measure.
How do you work out your own range?
Call it Wh in, miles out. You need the pack label, a loop of known length and a note on your phone.
- Battery energy. The pack label shows the voltage (V) and the capacity in amp-hours (Ah). Energy in watt-hours is V × Ah. Some labels print the Wh figure for you.
- Usable energy. The battery management system shuts the pack off before any cell runs too low, and you want to arrive with charge left over. Plan with less than the label figure.
- Your rate. Start with a full pack and ride your loop at one assist level. If the display or app shows energy used, divide it by the miles. If it only shows bars, take the share of the pack you used, multiply it by the pack's Wh and divide by the miles.
- Your range. Usable Wh ÷ your Wh per mile.
- Repeat. Ride the same loop on a cold morning, on a wet day and one level higher, and keep each result.
| Line on your worksheet | How you get it | What moves it |
|---|---|---|
| Battery energy (Wh) | V × Ah from the pack label | Shrinks slowly as the pack ages |
| Usable energy (Wh) | Battery energy minus the reserve you decide to keep | Your margin, and where the BMS cuts off |
| Wh per mile, dry and mild | Your loop, one assist level, a calm day | Assist level, weight, wind, tyre pressure |
| Wh per mile, a British winter month | The same loop on a cold morning | A cold pack gives less, and the lights stay on longer |
| Wh per mile, a wet ride | The same loop in rain | More braking and pulling away, lights on throughout |
| Range for a planned ride | Usable Wh ÷ the row that fits the day | Take the worst row if you cannot shorten the ride |
For the wet-day row, what changes when you ride in rain explains the extra stopping, starting and lighting. As a pack ages, the first line on the worksheet slowly falls, and how an e-bike battery wears with age lists the signs.
Which factors change your miles per charge?
- Assist level. Each step up adds more motor effort to every pedal stroke and more Wh to every mile. How the sensor and controller share out the help shows why.
- Weight. Rider, bags and anything on the rack all have to be moved, which you feel most when pulling away and uphill.
- Uphill stretches. Lifting bike and rider takes energy that a flat road does not ask for, and the ride back down returns very little of it.
- Wind. A headwind on the way out costs more than the tailwind on the way home gives back.
- Tyres. Soft or knobbly tyres roll less freely. Keep them at the pressure printed on the sidewall.
- Stop-start riding. Getting going from a standstill uses more than holding a steady pace.
- Cold. A lithium-ion pack usually gives less when it is cold, and the gauge can drop faster than you expect.
Why do the miles drop in winter?
A cold battery gives less, and a British winter adds its own costs: lights for more of the ride, more stops at junctions in the dark, heavier clothing on the rider. The DfT's e-cycle battery advice is to keep packs out of very hot, very cold or damp spots, charging above all. So bring the pack indoors between rides, give it time to lose its chill before charging, and read winter storage for a lithium battery if the bike will stand unused for weeks.
How should you read a very high range figure?
Very large mileage figures are possible on paper: a big pack, the lowest assist level, a light rider and flat, calm roads. Before you trust one, ask which assist level, rider weight, route and temperature it came from. If nobody can say, use your own worksheet. A bigger pack does add miles at the same rate of use, but it also adds weight and charging time.
The same sums work for a scooter, and our guide on how an e-scooter's range is worked out applies them to a deck and handlebar. Still deciding between the two? Our side-by-side of a scooter and an e-bike puts range next to storage and upkeep.
How do you plan a ride with charge to spare?
- Pick the worksheet row that matches the day, and plan with the worst one if you cannot cut the ride short.
- Decide on a reserve before you leave and treat it as untouchable.
- Ride a low level on the flat and save the higher ones for pulling away and uphill stretches.
- Check the forecast for wind, and ride into it while the pack is full.
- Charge the evening before, at a time when you are in and awake, then take the plug out once the gauge reads full.
- If the gauge runs low, drop a level early. If the pack does run out, you can still pedal home in a low gear; it is simply a heavier bike.
When lost range means stop
Some loss of range over the years is normal. Stop using the pack, disconnect the charger and ask the manufacturer, or the shop where you bought the bike, if:
- the range has dropped sharply from one week to the next in mild weather;
- the pack will not fill completely any more, or a charge now takes far longer than it did;
- the casing has swollen or split, or the pack runs unusually hot, makes hissing or crackling sounds, or starts to smell;
- the bike cuts out under load while the gauge still shows charge.
In Great Britain, an e-bike can be ridden like a pedal bike – on roads and cycle paths, without a licence, registration, tax or insurance – only if it is an electrically assisted pedal cycle (EAPC): it has pedals that drive it, its motor has a continuous rated power of no more than 250 W, and the motor stops assisting above 15.5 mph (25 km/h). You must be 14 or over to ride one on the road, and no e-bike may be ridden on the pavement.
Questions riders ask
Does a lower assist level give me more range?
Usually yes. On a lower level the motor adds less to each pedal stroke, so it draws less from the battery for every mile and you do more of the work. Drop a level on flat stretches and keep the higher ones for pulling away and going uphill.
Why does the range on my display keep changing?
Most displays estimate the miles left from how you have ridden over the last stretch. Ride uphill into a headwind and the estimate falls; cruise along a flat road and it rises. Treat it as a guide, and plan with the Wh per mile you have measured yourself.
Should I run the battery flat to find my range?
There is no need. Measuring how much of the gauge one known loop uses gives you the same answer, and you avoid being stranded far from home. The BMS will shut the pack off before the cells are drained, but follow the maker's instructions on how low to go.
Is a bigger battery worth the extra weight?
It depends on the furthest ride you do regularly. More watt-hours give more miles at the same rate of use, but the pack weighs more and takes longer to charge. If your rides already end with charge to spare, a bigger pack mostly adds weight you carry every time.
Do wide tyres reduce an e-bike's range?
Often a little. A wide, knobbly tyre at low pressure rolls less freely on tarmac than a narrower, smoother one inflated as its sidewall says, so it costs some Wh per mile. On loose ground the wide tyre can still be the better choice for grip.