Watt-hours (Wh) are the best single number for comparing e-bike batteries, because they combine voltage and amp-hours. Enter any two values from your battery label and the calculator works out the rest.
E-bike Battery Wh Calculator
Convert between volts, amp-hours, milliamp-hours and watt-hours.
How do you calculate e-bike battery watt-hours?
Multiply the battery’s nominal voltage by its amp-hours. The result is the total energy the battery stores.
Watt-hours (Wh) = Volts (V) × Amp-hours (Ah)
A 36V 14Ah battery holds 504Wh. A 48V 10Ah battery holds 480Wh. To go the other way, divide watt-hours by volts: a 500Wh battery at 36V is about 13.9Ah. This is the same formula the FAA uses to rate batteries for flights (FAA PackSafe).
Why compare batteries by Wh, not Ah?
Amp-hours alone are misleading when batteries have different voltages. A 48V 14Ah battery holds more energy than a 36V 14Ah battery, even though both say 14Ah.
| Battery | Amp-hours | Watt-hours |
|---|---|---|
| 36V 14Ah | 14Ah | 504Wh |
| 48V 14Ah | 14Ah | 672Wh |
| 48V 10.5Ah | 10.5Ah | 504Wh |
| 52V 17.5Ah | 17.5Ah | 910Wh |
The 36V 14Ah and 48V 10.5Ah packs hold the same energy, so with the same motor and rider they’d give similar range. Our guide on 36V vs 48V e-bike batteries explains what voltage does change, such as power delivery and charger choice.
What can I do with my battery’s watt-hours?
- Estimate range: divide watt-hours by your energy use per mile, or use the e-bike range calculator.
- Check flight rules: the e-bike battery flight checker compares watt-hours with the FAA limits.
- Compare replacements: a replacement with more Wh at the same voltage gives more range, as long as your bike’s maker approves it.
Where do I find my battery’s voltage and amp-hours?
Look on the battery’s label or casing. It usually lists nominal voltage (V) and capacity in Ah or mAh, and sometimes watt-hours. If you only see mAh, divide by 1,000 to get Ah: 14,000mAh is 14Ah.
Use the nominal voltage (for example 36V), not the charger’s higher output voltage (42V). The e-bike charger compatibility checker explains why those two numbers differ.
Frequently Asked Questions
Is a higher Ah battery always better?
Only at the same voltage. Compare watt-hours when voltages differ.
How many Wh is a 48V 13Ah battery?
48 × 13 = 624Wh.
How many Ah is a 500Wh 36V battery?
500 ÷ 36 ≈ 13.9Ah.
Should I use 42V or 36V in the formula?
Use the nominal voltage on the battery label (36V). 42V is the charger’s full-charge voltage.
Does more Wh mean a heavier battery?
Usually, since more energy needs more cells, but cell type and design also affect weight.