mAh to watt-hours, explained simply.
TSA caps power banks at 100 Wh — but most chargers are labeled in mAh. Here’s the conversion.
Watt-hours = (mAh ÷ 1000) × voltage.
Power banks are labeled in milliamp-hours (mAh). Airlines and TSA measure in watt-hours (Wh). The conversion: divide mAh by 1,000, multiply by voltage. For lithium-ion power banks, the cell voltage is almost always 3.7V.
Quick reference table.
5,000 mAh ≈ 18.5 Wh (Clutch Pro). 10,000 mAh ≈ 37 Wh. 15,000 mAh ≈ 55.5 Wh. 20,000 mAh ≈ 74 Wh. 27,000 mAh ≈ 100 Wh (the TSA ceiling). Anything bigger needs airline approval.
Lithium-ion chemistry.
A single lithium-ion cell has a nominal voltage of 3.7V. Even power banks with USB-C output at 5V, 9V, 12V, or 20V are still using 3.7V cells inside — the higher output voltages come from internal boost circuits. For TSA math, always use 3.7V.
When to double-check.
Under 18 Wh
Always allowed, no math required.
18–99 Wh
Allowed in carry-on. Includes most travel chargers.
100–160 Wh
Requires airline approval. Max two per passenger.
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The math is on your side.
Clutch Pro is 5,000 mAh — about 18.5 Wh. You’d need to multiply that by five before TSA would even raise an eyebrow.
Shop the Clutch ProFrequently asked
Why is my power bank labeled in mAh, not Wh?
mAh is the battery industry standard. Airlines measure in Wh because it captures total energy regardless of voltage. The conversion is straightforward: Wh = (mAh ÷ 1000) × voltage.
What voltage should I use for the math?
Always 3.7V for lithium-ion cells. Even if the power bank outputs at 5V or 20V via USB-C PD, the cells inside are still 3.7V.
Is a 20,000 mAh power bank allowed on planes?
Yes. 20,000 mAh × 3.7V ÷ 1,000 = 74 Wh, well under the 100 Wh limit.
What about 30,000 mAh?
30,000 mAh is approximately 111 Wh, which puts it in the 100–160 Wh range. You’ll need airline approval and a limit of two per passenger.
Reviewed by The Clutch Team · June 2026
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