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. Results are rounded for display; reversing uses full precision.
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 labelsDifferent voltages? Compare watt-hours, not just mAh.
Understand the conversion
From an Ah label to an energy budget
Ah alone does not tell you how much energy a battery stores. Voltage matters: increasing nominal voltage while keeping the Ah rating fixed increases the nominal energy in the same proportion.
Use the voltage of the complete battery or bank associated with the Ah rating. 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.
Unit reference: NIST conversion factors 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?
It is a starting energy figure. 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.