Watt-Hours to Amp-Hours Calculator
Convert energy in watt-hours (Wh) back to battery capacity in amp-hours (Ah) using the system voltage.
How to convert Wh to Ah
The formula is Ah = Wh / V.
For example, 1200 Wh at 12V = 100 Ah; the same 1200 Wh at 24V = 50 Ah. This shows why voltage is strictly required when determining capacity.
Common Wh to Ah Conversions
| Watt-Hours (Wh) | 12V System | 24V System | 48V System |
|---|---|---|---|
| 500 Wh | 41.67 Ah | 20.83 Ah | 10.42 Ah |
| 1000 Wh | 83.33 Ah | 41.67 Ah | 20.83 Ah |
| 1200 Wh | 100.00 Ah | 50.00 Ah | 25.00 Ah |
| 2000 Wh | 166.67 Ah | 83.33 Ah | 41.67 Ah |
| 5000 Wh | 416.67 Ah | 208.33 Ah | 104.17 Ah |
Comparing High-Tech Batteries to Lead-Acid
Modern lithium batteries (like those in solar generators and e-bikes) are rated in Watt-hours (Wh). Traditional lead-acid batteries (like RV and boat batteries) are rated in Amp-hours (Ah). Converting Wh back to Ah at 12 Volts lets you compare old and new technologies directly:
- Jackery Explorer 1000 Power Station (1,002 Wh):
Equivalent 12V Ah = 1,002 ÷ 12 = 83.5 Ah. This modern, lightweight power station stores slightly less total energy than a single, heavy 100Ah deep-cycle marine battery. - Tesla Powerwall 2 Home Battery (13,500 Wh):
Equivalent 48V Ah = 13,500 ÷ 48 = 281 Ah. To build an equivalent DIY off-grid battery bank at 48V, you would need nearly 300 Amp-hours of capacity. - Bosch E-Bike PowerTube (625 Wh at 36V):
Equivalent Ah = 625 ÷ 36 = 17.3 Ah. A common size for premium e-bikes, offering a balance of weight and long range.
Frequently Asked Questions
Why does the Ah change with voltage?
Amp-hours measure charge, while watt-hours measure total energy. To get the same total energy at a higher voltage, you need fewer amp-hours.
Can I convert without knowing voltage?
No, the conversion is meaningless without system voltage.
Is this used for lithium batteries?
Yes, but always use the nominal voltage (e.g. 12.8V for LiFePO4) for the most accurate calculation.