How the conversion works
Watt-hours are energy; amp-hours are charge. Multiplying charge by the battery's nominal voltage gives energy: Wh = Ah × V. The reverse, Ah = Wh ÷ V, converts an energy figure back to capacity at a chosen voltage.
For example, a 100 Ah battery at 12 V nominal stores 1,200 Wh. The same 1,200 Wh at 24 V corresponds to 50 Ah — which is why amp-hours alone cannot compare batteries of different voltages.
What the conversion does not tell you
The result is nominal stored energy, not what you can draw in practice. Usable energy depends on depth of discharge, and real voltage moves with the state of charge and load. For a runtime estimate that applies those factors, use the Battery Runtime calculator.
Typical nominal voltages
| Battery type | Nominal voltage | 100 Ah in Wh |
|---|---|---|
| Li-ion cell (NMC) | 3.6–3.7 V | 360–370 Wh |
| LiFePO4 cell | 3.2 V | 320 Wh |
| 12 V lead-acid / LiFePO4 pack | 12 V / 12.8 V | 1,200 / 1,280 Wh |
| 24 V system | 24 V | 2,400 Wh |
| 48 V system | 48 V | 4,800 Wh |
Common Ah to Wh and Wh to Ah conversions
The tables below are the same formula applied to the capacities and voltages people ask about most. Click a value to open it in the calculator with the numbers already filled in.
Amp-hours to watt-hours
| Capacity | at 12 V | at 24 V | at 48 V |
|---|---|---|---|
| 7 Ah | 84.0 Wh | 168 Wh | 336 Wh |
| 10 Ah | 120 Wh | 240 Wh | 480 Wh |
| 15 Ah | 180 Wh | 360 Wh | 720 Wh |
| 20 Ah | 240 Wh | 480 Wh | 960 Wh |
| 50 Ah | 600 Wh | 1,200 Wh | 2,400 Wh |
| 100 Ah | 1,200 Wh | 2,400 Wh | 4,800 Wh |
| 150 Ah | 1,800 Wh | 3,600 Wh | 7,200 Wh |
| 200 Ah | 2,400 Wh | 4,800 Wh | 9,600 Wh |
| 280 Ah | 3,360 Wh | 6,720 Wh | 13,440 Wh |
Watt-hours to amp-hours
Power banks and laptop batteries are usually rated at 3.7 V per cell, so a 27 Wh pack is about 7.3 Ah (7,300 mAh) of cell capacity. Airlines commonly allow up to 100 Wh in carry-on without approval and up to 160 Wh with it. Portable power stations are sold by watt-hours (1,024 Wh and 1,280 Wh are common sizes); a 12.8 V LiFePO4 battery of 100 Ah is the same 1,280 Wh.
| Energy | at 3.7 V | at 12 V | at 24 V |
|---|---|---|---|
| 27 Wh | 7.30 Ah | 2.25 Ah | 1.13 Ah |
| 50 Wh | 13.5 Ah | 4.17 Ah | 2.08 Ah |
| 100 Wh | 27.0 Ah | 8.33 Ah | 4.17 Ah |
| 160 Wh | 43.2 Ah | 13.3 Ah | 6.67 Ah |
| 500 Wh | 135 Ah | 41.7 Ah | 20.8 Ah |
| 1,000 Wh | 270 Ah | 83.3 Ah | 41.7 Ah |
| 1,024 Wh | 277 Ah | 85.3 Ah | 42.7 Ah |
| 1,200 Wh | 324 Ah | 100 Ah | 50.0 Ah |
| 1,280 Wh | 346 Ah | 107 Ah | 53.3 Ah |
| 2,000 Wh | 541 Ah | 167 Ah | 83.3 Ah |
Methodology
The conversion is exact for the voltage you enter; the judgement is in choosing that voltage. The calculator UI, examples and displayed formula all call the same conversion function.
- Wh = Ah × V — Definition of electrical energy and charge (SI units)
- Typical nominal voltages (3.2 V LiFePO4, 3.6–3.7 V Li-ion, 12/24/48 V systems) — Cell and battery manufacturer datasheets, e.g. EVE, Samsung SDI, Victron Energy
Assumptions last reviewed on 26 August 2026. If a source disagrees with your battery or equipment datasheet, trust the datasheet.
Frequently asked questions
Why do watt-hours matter more than amp-hours?
Amp-hours only compare batteries at the same voltage. Watt-hours measure actual energy, so they compare across voltages.
Which voltage should I use for the conversion?
Use the nominal (rated) voltage printed on the battery — for example 3.7 V for a Li-ion cell or 12.8 V for a 12 V LiFePO4 pack.
Is all of the converted energy usable?
No. Usable energy depends on depth of discharge, which the conversion itself does not apply.