Ah to Wh Calculator
Use this tool to convert battery capacity from amp-hours (Ah) to watt-hours (Wh). Formula: Wh = Ah × V.
If you work with batteries, solar systems, RV power banks, electric bikes, or backup power, you’ll eventually need to convert amp-hours (Ah) into watt-hours (Wh). Ah tells you charge capacity, while Wh tells you total energy. Since most appliances are rated in watts, Wh is usually the more practical unit for planning runtime.
What is Ah and what is Wh?
Amp-hours (Ah)
Amp-hours measure electric charge. A 100Ah battery can theoretically deliver 100 amps for one hour, or 10 amps for 10 hours (under ideal conditions).
Watt-hours (Wh)
Watt-hours measure energy. This unit combines current and voltage, making it easier to estimate how long a battery can power real devices like laptops, fridges, lights, or inverters.
Ah to Wh formula
The conversion is simple:
Watt-hours (Wh) = Amp-hours (Ah) × Voltage (V)
- 100Ah at 12V = 1200Wh
- 100Ah at 24V = 2400Wh
- 50Ah at 48V = 2400Wh
Notice that the same Ah value can represent very different total energy depending on voltage.
Step-by-step conversion
- Find your battery’s Ah rating (on label/spec sheet).
- Find the nominal voltage (12V, 24V, 48V, etc.).
- Multiply Ah by volts.
- Optionally apply system efficiency if power goes through an inverter/controller.
Nominal energy vs usable energy
Real systems lose energy due to inverter losses, wiring, temperature, and battery chemistry. That’s why this calculator includes efficiency.
- Nominal Wh: Ah × V
- Usable Wh: Nominal Wh × (Efficiency ÷ 100)
Example: 100Ah × 12V = 1200Wh nominal. At 90% system efficiency, usable energy is about 1080Wh.
Quick reference table
| Battery Size | Voltage | Nominal Energy |
|---|---|---|
| 50Ah | 12V | 600Wh |
| 100Ah | 12V | 1200Wh |
| 100Ah | 24V | 2400Wh |
| 200Ah | 12V | 2400Wh |
| 100Ah | 48V | 4800Wh |
Common mistakes to avoid
- Ignoring voltage: Ah without voltage does not tell total energy.
- Forgetting efficiency losses: Real usable energy is lower than nominal.
- Assuming 100% battery discharge: Many batteries should not be fully drained regularly.
- Mixing AC and DC ratings: Appliance wattage may include startup spikes.
Practical use cases
Solar and off-grid systems
Convert battery bank Ah ratings into Wh or kWh to match your daily energy consumption profile.
RV and van life power planning
Estimate how long your lights, fan, fridge, and electronics can run before recharge is needed.
DIY backup batteries
Compare battery options fairly even when Ah ratings are similar but voltages differ.
Final takeaway
Ah is useful, but Wh is what you need for real-world energy planning. Use the calculator above to quickly convert Ah to Wh, apply efficiency, and estimate runtime for your connected load.