Watt Hours to mAh Calculator
| Watt Hours | 3.7V (mAh) | 5V (mAh) | 7.4V (mAh) |
|---|---|---|---|
| 5 Wh | 1,351 | 1,000 | 676 |
| 10 Wh | 2,703 | 2,000 | 1,351 |
| 20 Wh | 5,405 | 4,000 | 2,703 |
| 50 Wh | 13,514 | 10,000 | 6,757 |
| 100 Wh | 27,027 | 20,000 | 13,514 |
How to Convert Watt Hours to Milliamp Hours
Wh to mAh Formula with Voltage Factor
The conversion formula is mAh = (Wh × 1000) ÷ V. The ×1000 factor converts amp hours to milliamp hours. At 3.7V (standard lithium cell voltage), 10Wh = 2,703 mAh.
3.7V Lithium Battery Standard Explained
Most lithium-ion cells have a nominal voltage of 3.7V (3.6-3.7V depending on chemistry). This is why phone batteries are typically rated at 3.7V or 3.85V. Multi-cell configurations use multiples: 7.4V (2S), 11.1V (3S).
Scientific Unit Conversion for Electronics
In SI units, 1 mAh = 3.6 coulombs, and 1 Wh = 3,600 joules. These conversions are essential in electronic design and battery compliance testing. For reverse conversion, see mAh to Wh.
Smartphone & Power Bank Energy Calculations
Battery Label Interpretation
Phone manufacturers often market battery size in mAh (e.g., 5000mAh) because larger numbers sound more impressive. However, Wh is a more accurate measure because it accounts for voltage.
Capacity Marketing vs Real Output
A 20,000mAh power bank at 3.7V contains 74Wh. When charging a phone at 5V, the effective output capacity is about 14,800mAh due to voltage conversion losses (~26% loss).
Online Conversion Calculator Examples
Common examples: iPhone 16 Pro (3.85V, 18.039Wh ≈ 4,685mAh), Samsung Galaxy S24 (3.86V, 17.4Wh ≈ 4,508mAh). Use our calculator for any device. For all battery formulas, visit battery conversion calculator.
Regulatory Limits for mAh and Wh Ratings
Airline Travel Battery Restrictions
Airlines limit lithium batteries to 100Wh for carry-on (no check-in). Spare batteries 100-160Wh require airline approval. A 27,000mAh @ 3.7V power bank = 99.9Wh — just under the limit. For related conversions, see Wh to milliamp hours.
International Shipping Regulations
UN3481 (lithium-ion batteries packed with equipment) requires Wh labeling. IATA DGR Section II limits standalone shipment to 100Wh per cell. Always verify Wh ratings before shipping electronics internationally.