mAh to Wh Converter
Use this calculator to convert milliamp-hours (mAh) to watt-hours (Wh). Enter your battery capacity and voltage, then click calculate.
What this calculator does
This mAh to watt hour calculator converts battery capacity from milliamp-hours (mAh) into watt-hours (Wh), which is the standard unit for stored energy. If you are comparing power banks, phone batteries, drone packs, or airline battery limits, Wh gives you a more apples-to-apples number.
Wh = (mAh × V) ÷ 1000
Why mAh alone is not enough
Many people look only at mAh when buying a battery, but mAh measures charge, not energy. Two batteries can have the same mAh rating and different voltages, which means they store different amounts of energy.
- 10,000 mAh at 3.7V = 37 Wh
- 10,000 mAh at 5V = 50 Wh
Same mAh, different Wh. That is why voltage is required for an accurate conversion.
How to use the mAh to Wh calculator
Step 1: Enter mAh
Type your battery capacity in milliamp-hours. Example values: 2000, 5000, 10000, 26800.
Step 2: Enter voltage
Use the nominal voltage from the battery label or datasheet. For many lithium-ion cells, 3.7V is common. If you are unsure, use one of the voltage presets to quickly fill the field.
Step 3: Click Calculate Wh
The calculator will display watt-hours, amp-hours, and kilowatt-hours so you can compare battery energy in different contexts.
Common mAh to Wh examples
At 3.7V (typical Li-ion nominal)
- 1,000 mAh = 3.7 Wh
- 5,000 mAh = 18.5 Wh
- 10,000 mAh = 37 Wh
- 20,000 mAh = 74 Wh
- 26,800 mAh = 99.16 Wh
At 5V (USB output reference)
- 1,000 mAh = 5 Wh
- 5,000 mAh = 25 Wh
- 10,000 mAh = 50 Wh
- 20,000 mAh = 100 Wh
Travel and airline battery limits
Airline rules are often written in watt-hours, not mAh. A commonly referenced threshold is 100 Wh for carry-on batteries. Because rules vary by airline and country, always check your carrier’s latest policy before flying.
This converter helps you estimate quickly: if your battery is close to 100 Wh, calculate it before your trip.
Important practical notes
- Use nominal voltage: Most battery labels use nominal voltage, not full-charge voltage.
- Output conversion losses: Power banks lose some energy during voltage conversion, so delivered energy is lower.
- Round carefully: For compliance or shipping forms, keep enough decimal precision.
- Check manufacturer specs: When available, manufacturer-rated Wh is the authoritative figure.
FAQ
Is mAh bigger always better?
Higher mAh can mean more stored charge, but only at a known voltage can you compare real energy. Use Wh for fair comparisons.
Can I convert Wh back to mAh?
Yes. Rearranging the same formula gives:
mAh = (Wh × 1000) ÷ V
Why does my power bank say 10,000 mAh but charge my phone less than expected?
Losses occur in voltage conversion, cable resistance, device charging circuitry, and battery aging. The full rated energy is not delivered as usable output.
Bottom line
If you want a quick, accurate battery energy conversion, this mAh to watt hour calculator is all you need: enter mAh, enter voltage, and calculate. For shopping, technical comparisons, and travel checks, watt-hours are the clearest metric.