Battery Capacity Calculator — mAh to Wh Converter
Enter a battery's capacity in mAh and its nominal voltage to convert to watt-hours (Wh), joules and kWh — and instantly check whether it exceeds the IATA 100 Wh carry-on limit for air travel.
mAh
V
%
Watt-hours = mAh × V ÷ 1000 — the standard measure for battery size
- 1
Raw energy (mWh)
5,000 mAh × 3.7 V = 18,500 mWh - 2
Energy in Wh
18,500 mWh ÷ 1000 = 18.50Dividing by 1000 converts milliwatt-hours to watt-hours.
How does this calculator work?
Energy (Wh) = mAh × Voltage ÷ 1 000. A 5 000 mAh Li-ion at 3.7 V holds 18.5 Wh. Multiply Wh by 3 600 for joules, divide by 1 000 for kWh. IATA allows up to 100 Wh per battery in cabin carry-on without special approval — most phone power banks fall well below this limit.
Formula
How this is calculated
Battery capacity in mAh (milliampere-hours) tells you how much charge a battery holds at a given current draw, but it says nothing about energy unless you also know the voltage. Energy in watt-hours (Wh) combines both: Wh = mAh × V ÷ 1000. A 5 000 mAh phone battery at 3.7 V holds 18.5 Wh — about the same as leaving a 20 W bulb on for 55 minutes.
Watt-hours are the universal comparison metric: they appear on power banks, tool batteries, e-bike packs and EV specs. Joules (J = Wh × 3 600) are the SI unit used in physics and safety datasheets. kWh (Wh ÷ 1 000) is the unit on your electricity bill, useful for costing recharge.
For air travel, IATA regulations allow Li-ion batteries up to 100 Wh per battery in carry-on without special approval; 100–160 Wh requires airline approval; above 160 Wh is generally forbidden in passenger cabins. The calculator flags where your battery sits relative to the 100 Wh threshold.
Frequently asked questions
mAh measures charge (coulombs × time), not energy. Energy = charge × voltage. A 10 000 mAh battery at 3.7 V stores 37 Wh, but the same 10 000 mAh pack at 7.4 V (two cells in series) stores 74 Wh — double the energy. Always check the nominal voltage on the label.
IATA rules allow Li-ion batteries up to 100 Wh per battery in cabin carry-on baggage without any special approval. Between 100 and 160 Wh you need airline approval and are limited to two batteries. Above 160 Wh is generally prohibited. Most phone power banks (10 000 mAh at 3.7 V ≈ 37 Wh) are well under the limit.
Common nominal voltages: Li-ion / Li-Po cell ≈ 3.6–3.7 V; LiFePO₄ cell ≈ 3.2 V; NiMH / NiCd AA ≈ 1.2 V; alkaline AA ≈ 1.5 V; lead-acid cell ≈ 2.0 V. Tool packs and e-bike packs are multiple cells in series — divide pack voltage by cell count (or check the label).
TG we-Calculate Editorial Team. (2026). Battery Capacity Calculator — mAh to Wh Converter [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/battery-capacity-calculator
TG we-Calculate Editorial Team. "Battery Capacity Calculator — mAh to Wh Converter." TG we-Calculate. 2026. https://we-calculate.com/calculator/battery-capacity-calculator.
TG we-Calculate Editorial Team, "Battery Capacity Calculator — mAh to Wh Converter," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/battery-capacity-calculator
@misc{wecalculate_battery_capacity_calculator, title = {Battery Capacity Calculator — mAh to Wh Converter}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/battery-capacity-calculator}}, year = {2026}, note = {TG we-Calculate} }
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