Ah to kWh calculator
Multiply amp-hours by nominal voltage and divide by 1,000. A 100 Ah battery at 12.8 V is 1.28 kWh. At 51.2 V, the same 100 Ah rating is 5.12 kWh.
100 Ah at 12.8 volts equals 1.28 kWh.
100 Ah at 12.8 V
Nominal stored energy
100 × 12.8 ÷ 1,000 = 1.28 kWh
- mAh
- 100,000
- Ah
- 100
- Wh
- 1,280
- kWh
- 1.28
These values describe the same battery rating at 12.8 V. We round the displayed values but keep the full result when you reverse the conversion.
A 10,000 mAh rating at 3.7 V is 37 Wh. At 7.4 V, the same charge capacity is 74 Wh. Check the battery label before changing the voltage.
Compare two battery labelsUse watt-hours to compare batteries at different voltages.
Understand the conversion
How voltage affects the kWh rating
To find a battery’s energy from its Ah rating, you need its nominal voltage. Double the voltage at the same Ah rating and you double the nominal energy.
Use the voltage of the complete battery or bank whose Ah rating you are converting. For matched 12.8 V, 100 Ah batteries, two in series give 25.6 V at 100 Ah; two in parallel give 12.8 V at 200 Ah. Both arrangements have 2.56 kWh of nominal energy.
Formula and worked example
kWh = Ah × V ÷ 1,000
Ah = kWh × 1,000 ÷ V
100 Ah × 12.8 V ÷ 1,000 = 1.28 kWh. At 51.2 V: 100 Ah × 51.2 V ÷ 1,000 = 5.12 kWh.
The NIST conversion reference lists ampere-hours under electric charge and watt-hours under energy. The battery calculations here use nominal label voltage.
100 Ah converted to kWh by voltage
Use the exact nominal voltage on the label, including 12.8 V or 51.2 V when specified. This reference table stays fixed while you edit the calculator.
| Ah | Nominal voltage | kWh |
|---|---|---|
| 100 | 12 V | 1.2 |
| 100 | 12.8 V | 1.28 |
| 100 | 24 V | 2.4 |
| 100 | 25.6 V | 2.56 |
| 100 | 36 V | 3.6 |
| 100 | 48 V | 4.8 |
| 100 | 51.2 V | 5.12 |
Common questions
Which voltage should I use?
Use the nominal voltage printed with the capacity rating. For a pack rating, use the pack voltage. For a single cell, use the cell voltage. A charger's full-charge voltage or a USB port's output voltage may describe a different part of the system.
How many kWh is a 100 Ah battery?
It depends on voltage. A 100 Ah rating gives 1.2 kWh at 12 V, 1.28 kWh at 12.8 V, and 4.8 kWh at 48 V.
Can I use the kWh result to estimate runtime?
Use it as a starting point. Divide usable Wh by load watts for an ideal runtime in hours. The runtime tool lets you account for more of the conditions that change usable energy.