How to Calculate Watt-Hours (Wh) for Your Power Bank or Energy Bank

Most airlines restrict the transport of Power Banks or other devices containing lithium-ion or lithium-metal batteries. It’s essential to know how to convert milliamp-hours (mAh) into watt-hours (Wh), as airline regulations are based on Wh, not mAh.

For example, you can check airBaltic's baggage policy here – airBaltic baggage restrictions.

Formula to Calculate Wh for Power Banks

(mAh) / 1000 × (V) = (Wh)

Milliamp-hours divided by 1000, multiplied by nominal voltage = watt-hours

Explanation:

• mAh – how long the battery can supply current.
• V – nominal voltage (typically 3.7V for lithium-ion cells).
• Wh – energy unit indicating how many watts are delivered in an hour.

Examples:

• 10000 mAh / 1000 × 3.7 V = 37 Wh
• 20000 mAh / 1000 × 3.7 V = 74 Wh

These are below the 100 Wh limit and are allowed on most airlines.

If Voltage is Unknown:

If the battery type is unknown, you can use the default USB output voltage – 5V:

(mAh) / 1000 × 5V = Wh

For example: 20000 mAh × 5V / 1000 = 100 Wh – the maximum allowed by most airlines.

Tip: Always verify your Power Bank's Wh rating before traveling to avoid issues at the airport.