Case 1
- Battery capacity
- 10000mAh
- Nominal pack voltage
- 3.7V
37.00Wh
Open with these valuesmAh to Wh Calculator
37.00Wh
Result: 37.00 WhMultiply the capacity in mAh by the nominal voltage and divide by 1000. A 10,000 mAh power bank at 3.7 V holds 37 Wh — comfortably under the 100 Wh that airlines allow in carry-on baggage without approval. mAh alone says nothing about energy until you know the voltage.
The numbers at a glance
Held fixed: Battery capacity 10,000 mAh.
| Nominal pack voltage (V) | Result (Wh) |
|---|---|
| 1.00 | 10.00 |
| 2.00 | 20.00 |
| 3.00 | 30.00 |
| 3.70Your value | 37.00 |
| 4.00 | 40.00 |
| 5.00 | 50.00 |
| 6.00 | 60.00 |
| 7.00 | 70.00 |
Worked examples
Case 2
- Battery capacity
- 3000mAh
- Nominal pack voltage
- 11.1V
33.30Wh
Open with these valuesCase 3
- Battery capacity
- 100000mAh
- Nominal pack voltage
- 12V
1,200.00Wh
Open with these valuesHow it's calculated
Wh = (mAh × V) ÷ 1000
- StepRead the mAh figure printed on the battery or power bank.
- StepEnter the nominal pack voltage — about 3.7 V for one Li-ion cell.
- ResultRead the energy in watt-hours and compare it with the 100 Wh limit.
Reference table
| Capacity, voltage | Battery | Energy |
|---|---|---|
| 5000, 3.7 | Compact phone power bank | 18.5 |
| 3000, 11.1 | Three-cell hobby pack | 33.3 |
| 10000, 3.7 | Standard phone power bank | 37 |
| 20000, 3.7 | Large power bank | 74 |
| 100000, 12 | Portable power station | 1200 |
Questions
How do I convert mAh to Wh?
Multiply the capacity in milliamp-hours by the nominal voltage and divide by 1000: Wh = (mAh × V) ÷ 1000. A 10,000 mAh power bank at 3.7 V holds (10,000 × 3.7) ÷ 1000 = 37 Wh.
Why do I need the voltage to get watt-hours?
mAh alone measures charge, not energy. Watt-hours combine charge with voltage, so two packs with the same mAh but different voltages store different amounts of energy.
What voltage should I enter for a power bank?
The nominal cell voltage, about 3.7 V for lithium-ion. Most phone power banks are rated at the cell voltage even though their USB output is 5 V, so 3.7 V usually reproduces the Wh figure on the label. Three cells in series make about 11.1 V.
How does this relate to airline carry-on limits?
Aviation rules cap lithium batteries by watt-hours, not mAh — typically 100 Wh per battery without airline approval. A 10,000 mAh pack at 3.7 V is 37 Wh, while a 27,000 mAh pack at the same voltage sits right at about 100 Wh.
What is the difference between Wh and kWh?
A kilowatt-hour is 1000 watt-hours, so divide by 1000 to get from one to the other. A 37 Wh power bank is 0.037 kWh; kilowatt-hours are the unit for home energy and electric cars.
Sources and last check
Information, not professional advice.