Amp-hours to watt-hours calculator
Watt-hours = amp-hours × volts. Watt-hours let you compare batteries of different voltages, power stations and loads on the same scale; usable watt-hours tell you what you can actually take out.
Enter your measurements
More options: DoD
- In kWh
- 1.2 kWh
- Usable energy at your depth of discharge
- 960 Wh
- Usable amp-hours
- 80 Ah
100 Ah × 12 V = 1,200 Wh (1.2 kWh)
Usable at 80% depth of discharge: 960 Wh (80 Ah)
- A “12 V” LiFePO4 battery is 12.8 V nominal, so 100 Ah is about 1,280 Wh rather than 1,200. Switch the voltage to 12.8 if the label says so.
Quick answers for common sizes
| Example | Answer |
|---|---|
| How many watt-hours in a 100Ah battery | 1,280 Wh (12.8 V LiFePO4) or 1,200 Wh (12 V lead-acid) |
| How many watt-hours in a 200Ah battery | 2,560 Wh (12.8 V LiFePO4) or 2,400 Wh (12 V lead-acid) |
| A 48V 100Ah battery in kWh | 5.12 kWh (about 4.1 kWh usable) |
Common battery sizes at the voltage above
| Battery capacity | Energy | In kWh | Usable energy at your depth of discharge |
|---|---|---|---|
| 50 | 600 Wh | 0.6 kWh | 480 Wh |
| 100 | 1,200 Wh | 1.2 kWh | 960 Wh |
| 200 | 2,400 Wh | 2.4 kWh | 1,920 Wh |
| 280 | 3,360 Wh | 3.36 kWh | 2,688 Wh |
| 300 | 3,600 Wh | 3.6 kWh | 2,880 Wh |
| 400 | 4,800 Wh | 4.8 kWh | 3,840 Wh |
The sizes people ask about are worked out on their own pages: how many watt-hours in a 100Ah battery, how many watt-hours in a 200Ah battery and a 48V 100Ah battery in kWh.
The formula
Amp-hours measure charge: how many amps a battery can deliver for how many hours. Watt-hours measure energy, which also depends on voltage. A 12 V 100 Ah battery and a 24 V 100 Ah battery have the same amp-hours but the 24 V one holds twice the energy.
Wh = Ah × V Ah = Wh ÷ V kWh = Wh ÷ 1,000 usable Wh = Wh × depth of discharge
Why “usable” is smaller
Planning on the full label rating runs batteries harder than their makers intend. Victron rates its LiFePO4 batteries for 2,500 cycles at 80% depth of discharge (5,000 at 50%). Trojan recommends discharging its lead-acid batteries 20–50% for best life, though they can be cycled to 80%. So the default here is 80% usable for LiFePO4 and 50% for lead-acid; change it under More options if your battery’s data sheet says otherwise.
| Battery | Rated energy | Usable (default) |
|---|---|---|
| 12 V 100 Ah lead-acid | 1,200 Wh | 600 Wh (50%) |
| 12.8 V 100 Ah LiFePO4 | 1,280 Wh | 1,024 Wh (80%) |
| 12.8 V 200 Ah LiFePO4 | 2,560 Wh | 2,048 Wh (80%) |
| 25.6 V 100 Ah LiFePO4 | 2,560 Wh | 2,048 Wh (80%) |
| 51.2 V 100 Ah LiFePO4 | 5,120 Wh | 4,096 Wh (80%) |
Group-size batteries hold different amp-hours depending on make and type — the battery group size chart lists group 24, 27 and 31 capacities from manufacturer data sheets.
Comparing a power station with a battery
Portable power stations are rated in watt-hours, batteries in amp-hours. Convert one to the other before you compare prices: a 1,024 Wh power station holds about the same energy as a 12.8 V 80 Ah LiFePO4 battery. Remember the power station loses some of that in its inverter — see the power station runtime calculator.
CalculatorBattery Runtime Calculator →How long will it run a fridge, a CPAP or an inverter load?What you’ll need
- 12 V 100 Ah LiFePO4 batteryPremium price
About 1.28 kWh rated in a box roughly the size of a group 24–31 lead-acid battery at around half the weight. Check the BMS discharge limit and whether it can charge below freezing.
See options on Amazon (opens in a new tab) - Battery monitor with shuntMid-range price
Counts amp-hours in and out, so you see true state of charge instead of guessing from voltage — which barely moves on a LiFePO4 battery until it is nearly empty.
See options on Amazon (opens in a new tab) - 12 V deep cycle AGM batteryMid-range price
Sealed lead-acid with no watering. Cheaper up front than lithium, but plan to use only about half its rating and expect it to weigh roughly twice as much.
See options on Amazon (opens in a new tab)
As an Amazon Associate we earn from qualifying purchases. Links to products are affiliate links — they cost you nothing extra and help keep these calculators free.
Frequently asked questions
How many watt-hours is a 100Ah battery?
1,200 Wh at 12 V for lead-acid, 1,280 Wh for a 12.8 V LiFePO4. Usable energy is about 600 Wh and 1,024 Wh at the default depths of discharge — see how many watt-hours in a 100Ah battery.
How do I convert watt-hours to amp-hours?
Divide by the voltage. A 1,000 Wh power station is about 78 Ah at 12.8 V or 83 Ah at 12 V.
How many kWh is a 200Ah battery?
2.4 kWh at 12 V, 2.56 kWh at 12.8 V, and 9.6–10.24 kWh at 48–51.2 V. See how many watt-hours in a 200Ah battery.
Are two 12 V 100 Ah batteries in series 200 Ah?
No — in series you get 24 V and 100 Ah (2,400 Wh). In parallel you get 12 V and 200 Ah (also 2,400 Wh). The energy is the same either way; only the voltage and amp-hours trade places.
Related guides
Sources
- Victron Energy — Lithium Battery Smart manual, technical data (opens in a new tab) — LiFePO4 12.8 V: cycle life 2,500 at 80% DoD, 3,000 at 70%, 5,000 at 50% (to 80% of capacity); 92% round-trip efficiency; 12.8 V 100 Ah: recommended continuous discharge ≤100 A (1C), maximum 200 A; capacity about 20% lower at 0 °C; charge only between +5 °C and +50 °C.
- Trojan Battery — Technical support FAQs (opens in a new tab) — “We generally recommend a discharge of 20 to 50% of the battery’s rated capacity even though the battery is capable of being cycled to 80%”; 20-hour and 100-hour ratings; freezing points by state of charge.
- Trojan Battery — 27TMX data sheet (opens in a new tab) — Group 27 flooded: 85 Ah (5-hr), 97 Ah (10-hr), 105 Ah (20-hr), 117 Ah (100-hr); state of charge vs open-circuit voltage table; charger settings.
- Crown Battery — Deep Cycle Battery Product Specifications (effective Oct 1, 2024) (opens in a new tab) — 20-hour capacities by BCI group for flooded, AGM and lithium 12 V batteries.