Convert mAh to Wh
Use this tool to convert battery capacity from milliamp-hours (mAh) to watt-hours (Wh).
What does mAh to Wh conversion mean?
Battery capacity is often listed in mAh (milliamp-hours), but many technical standards (and airline rules) use Wh (watt-hours). A mAh value tells you how much current a battery can supply over time, while a Wh value tells you total energy.
Because batteries can have different voltages, two batteries with the same mAh rating may store very different amounts of energy. That is why voltage must be included in the conversion.
mAh to Wh formula
The standard conversion is straightforward:
- Wh = (mAh × V) ÷ 1000
- mAh = (Wh × 1000) ÷ V (if converting in reverse)
If your battery is rated at 10,000 mAh and 3.7 V, then:
Wh = (10,000 × 3.7) ÷ 1000 = 37 Wh
Why voltage matters
Voltage is the missing piece most people overlook. Manufacturers sometimes market power banks only by mAh, but mAh alone cannot describe total energy. A higher-voltage system can produce more watt-hours from the same mAh number.
| Capacity (mAh) | Voltage (V) | Energy (Wh) |
|---|---|---|
| 5,000 | 3.7 | 18.5 |
| 5,000 | 5.0 | 25.0 |
| 20,000 | 3.7 | 74.0 |
Common use cases
1) Checking airline battery limits
Airlines often allow personal batteries below specific Wh thresholds (commonly 100 Wh for carry-on without special approval). If your battery label only shows mAh, this calculator helps you estimate whether it falls under that limit.
2) Comparing power banks fairly
If two brands advertise different voltage outputs or battery chemistry, convert both to Wh to compare true stored energy.
3) Estimating runtime
After converting to Wh, you can estimate runtime by dividing by your device power draw:
- Runtime (hours) ≈ Battery Wh ÷ Device Watts
- Example: 37 Wh battery powering a 10 W load ≈ 3.7 hours (ideal conditions)
Important notes for accurate calculations
- Use the battery's nominal voltage when possible (often 3.6 V or 3.7 V for Li-ion cells).
- Real-world usable energy is usually lower due to conversion losses and temperature.
- For packs with multiple cells, use the voltage listed for the full pack rating.
- If label data conflicts, prioritize manufacturer specs in Wh when available.
FAQ
Is mAh bigger than Wh?
They measure different things. mAh measures charge capacity; Wh measures energy. You cannot directly compare them without voltage.
Can I convert mAh to Wh without voltage?
No. Voltage is required. Without voltage, the conversion is incomplete.
Why does my calculated Wh differ from product packaging?
Differences can come from nominal voltage assumptions, rounding, internal circuitry losses, or manufacturer labeling conventions.
Final takeaway
For battery comparisons, travel checks, and runtime planning, Wh is the most useful unit. Use the calculator above to convert mAh to Wh in seconds and make better battery decisions with confidence.