Calculate your battery's Wh
If Wh is printed, use it instead of calculating.
Use nominal pack voltage, not full-charge voltage.
Enter Wh, or enter both mAh and nominal voltage.
A calculated number is a planning aid. It does not create or replace a manufacturer rating printed on the battery or official product documentation.
The formula
Wh = (mAh × nominal voltage) ÷ 1000
Example: a 6S 5000 mAh LiPo with a nominal 22.2 V rating is 111 Wh. That puts it in the 101–160 Wh band, which generally requires prior airline approval and is limited to two spare batteries.
Use nominal voltage, not charger output
Use the battery pack's nominal voltage. Do not multiply mAh by a USB charger output voltage or by the fully charged pack voltage unless the battery manufacturer specifically uses that figure for its Wh rating.
Prefer the printed Wh rating
If the manufacturer prints Wh on the battery, use that official rating. The checker supports direct Wh entry for this reason.