20,000mAh alone cannot establish watt-hours. You need the battery voltage used for that capacity rating. Read a printed Wh value first, then use values with the same basis if calculating.
Two steps for the conversion
The FAA guide gives Wh as Ah multiplied by battery voltage. Divide mAh by 1,000 to obtain Ah. This article uses only the unit arithmetic from the 2022 guide, not its old transport provisions as today’s passenger rules.
| Fictional matching ratings | Value |
|---|---|
| Capacity | 20,000mAh = 20Ah |
| Rated battery voltage | 3.7V |
| Energy | 20 × 3.7 = 74Wh |
Separate output voltage from battery voltage
Do not automatically multiply the front capacity by USB 5V in an output table. Find the battery voltage that defines that mAh rating. If absent, request a specification rather than assuming 3.7V. Clarify the rating basis if calculated and printed Wh differ.
74Wh does not promise a charge count
Wh starts an energy comparison. This fictional calculation includes neither conversion losses nor measured output. Do not divide phone and bank mAh to guarantee full charges. For travel, check current airline and airport instructions separately.
A worked example
Your record sheet: model, printed Wh, voltage associated with capacity, and input/output table. Photograph each. Leave calculation as “needs verification” when the matching voltage is unavailable; do not copy the example’s 3.7V into your specification.
Common questions
Is 20,000mAh always 74Wh?
No. This example assumes its matching battery voltage is 3.7V.
Does this calculation approve cabin carriage?
No. Check current rules and airline conditions separately.