mAh to Wh calculator for power banks
Convert mAh to Wh (and back) and check a power bank against the airline limit.
About this tool
Quick answer: To convert mAh to Wh, multiply by the battery voltage (usually 3.7 V) and divide by 1,000. A 10,000 mAh power bank is about 37 Wh, and a 20,000 mAh one about 74 Wh, both under the usual 100 Wh carry-on limit. Airlines limit batteries by Wh, not mAh.
How to use it
- Choose mAh to Wh, Wh to mAh, or Ah to mAh and Wh.
- Enter the capacity. Leave the voltage at 3.7 V unless the label says otherwise.
- Optional: enter your phone's battery size to see roughly how many charges you get.
Common power bank sizes (at 3.7 V)
| 5,000 mAh | 18.5 Wh |
|---|---|
| 10,000 mAh | 37 Wh |
| 20,000 mAh | 74 Wh |
| 25,000 mAh | 92.5 Wh |
| 30,000 mAh | 111 Wh (over the usual 100 Wh limit) |
| 50,000 mAh | 185 Wh (over the 160 Wh limit) |
1 Ah is 1,000 mAh, so a 5 Ah battery is 5,000 mAh.
Good to know
Why watt-hours matter on a plane
The common rule is that batteries up to 100 Wh may go in carry-on bags, 100 to 160 Wh need the airline's approval (usually limited to two), and larger ones are not allowed. Power banks go in carry-on bags, not checked luggage. Rules differ by airline and country, so check yours.
How many phone charges you really get
Some energy is lost as heat and in converting voltage, so you get roughly 60 to 80 percent of the rated capacity. A 10,000 mAh power bank usually charges a 4,500 mAh phone about one and a half times.
Check the label
If the power bank prints a watt-hour figure, use that. It is more reliable than the mAh number on the box.
Frequently asked questions
Can I take a 20,000 mAh power bank on a plane?
A typical 20,000 mAh power bank is about 74 Wh, which is under the common 100 Wh limit for carry-on bags. Always check the Wh rating on the label and your airline's rules.
How do I convert 10,000 mAh to Wh?
Multiply 10,000 by 3.7 volts and divide by 1,000. The result is 37 Wh.
Why is my power bank's real capacity lower than the number on the box?
Some energy is lost when the power bank boosts the battery voltage and charges your phone, usually 20 to 40 percent. Some products also overstate their rated capacity.
Does this calculator store what I type?
No. The maths runs in your browser and nothing is sent or saved.
Related reading
More tools
This tool uses only the numbers you type. It does not use or show Amazon product data, and nothing you enter is stored or sent.