How mAh to Wh conversion works
mAh (milliamp-hours) measures electric charge — current over time — not energy. Multiplying charge by voltage gives energy, the basic Ah × V = Wh relationship, so dividing by 1000 first converts mAh to Ah.
- mAh — battery capacity in milliamp-hours
- V — voltage (V) — 3.7V is standard for a single lithium-ion cell
- 1000 — converts mAh to Ah (1000 mAh = 1 Ah)
Common values
| Capacity (mAh) | Energy (Wh) |
|---|---|
| 300 mAh | 1.11 Wh |
| 750 mAh | 2.78 Wh |
| 1,500 mAh | 5.55 Wh |
| 3,000 mAh | 11.10 Wh |
| 4,500 mAh | 16.65 Wh |
| 6,000 mAh | 22.20 Wh |
| 9,000 mAh | 33.30 Wh |
| 15,000 mAh | 55.50 Wh |
| 30,000 mAh | 111.00 Wh |
More detail
Why mAh alone can't compare batteries
mAh is charge, not energy, so two batteries with the same mAh can hold very different amounts of power if their voltage differs. A 5000mAh cell at 3.7V holds 18.5Wh, but a 5000mAh pack wired for 7.4V (two cells in series) holds 37Wh — double the energy for the same mAh number. Comparing devices fairly means converting both to Wh first.
Practical tip. Multi-cell packs — laptops, power tools, e-bikes — report the pack's combined voltage, not the 3.7V of a single lithium-ion cell: 7.4V for 2 cells in series, 11.1V for 3. Check the label for the actual pack voltage before converting.
Frequently asked questions
How many Wh is a 3000mAh, 3.7V battery?
Wh = mAh × V ÷ 1000 = 3000 × 3.7 ÷ 1000 = 11.1Wh. Enter capacity 3000mAh and voltage 3.7V (the default) above to see the same result.
Why can't I compare batteries by mAh alone?
mAh only measures charge (current × time), not energy. A 5000mAh battery at 3.7V holds 18.5Wh, but the same 5000mAh at 7.4V (a 2-cell series pack) holds 37Wh — twice the energy. Converting both to Wh with this calculator is the fair comparison.
What voltage should I use if I don't know it?
3.7V — the nominal voltage of a single lithium-ion cell used in phones and most power banks — is the default. Multi-cell packs like laptop batteries typically use 7.4V (2 cells) or 11.1V (3 cells); check the product label for the exact figure.
Why does the result show "—" instead of a number?
In Wh = mAh × V ÷ 1000, if capacity or voltage is 0 or negative the energy amount isn't defined, so the calculator shows "—". Enter the actual mAh and V figures from the battery's spec label to get a valid result.