Wh to mAh Converter
Quick fact: To convert watt-hours to milliamp-hours, multiply Wh by 1,000 and divide by the battery voltage. The result depends on the voltage of the battery.
Frequently Asked Questions
How do I convert Wh to mAh?
Multiply the watt-hours (Wh) by 1,000, then divide by the battery voltage (V):
Example: 10 Wh at 3.7V = 10 × 1,000 / 3.7 = 2,702.7 mAh
How many mAh is 100 Wh?
It depends on voltage:
- At 3.7V (Li-ion): 100 × 1,000 / 3.7 = 27,027 mAh
- At 12V (Lead-acid): 100 × 1,000 / 12 = 8,333 mAh
- At 1.5V (Alkaline): 100 × 1,000 / 1.5 = 66,667 mAh
Why do power banks list mAh instead of Wh?
Marketing convention. mAh produces bigger, more impressive-sounding numbers. A 20,000 mAh power bank at 3.7V is actually only 74 Wh of usable energy.
Wh is a more accurate measure of total energy capacity because it accounts for voltage. Airlines and shipping regulations use Wh, not mAh.
What is the FAA battery limit in mAh?
The FAA limit is 100 Wh, which equals approximately 27,027 mAh at 3.7V. Key rules:
- Under 100 Wh: Carry-on allowed, no approval needed
- 100–160 Wh: Carry-on with airline approval
- Over 160 Wh: Prohibited on passenger aircraft
How to Convert Wh to mAh
Converting watt-hours to milliamp-hours requires knowing the battery voltage:
- Identify the battery voltage. Check the battery label for nominal voltage. Common values: 3.7V (Li-ion), 1.5V (alkaline), 1.2V (NiMH), 12V (lead-acid).
- Apply the formula: mAh = Wh × 1,000 / V
- Read the result. Higher voltage means fewer mAh for the same energy.
Example: A laptop battery rated at 56 Wh with a 7.4V pack:
56 × 1,000 / 7.4 = 7,568 mAh
Wh to mAh Formula
Where:
- Wh = watt-hours (energy capacity)
- V = nominal voltage of the battery
- mAh = milliamp-hours (charge capacity)
This works because Wh = V × Ah, and Ah × 1,000 = mAh. Rearranging: mAh = Wh / V × 1,000.
Common Battery Capacities
| Battery Type | Voltage | Typical mAh | Typical Wh |
|---|---|---|---|
| AA Alkaline | 1.5V | 2,500 mAh | 3.75 Wh |
| AA NiMH Rechargeable | 1.2V | 2,000 mAh | 2.4 Wh |
| 18650 Li-ion | 3.7V | 2,500–3,500 mAh | 9.25–12.95 Wh |
| Smartphone | 3.7V | 3,000–5,000 mAh | 11.1–18.5 Wh |
| Power Bank (small) | 3.7V | 10,000 mAh | 37 Wh |
| Power Bank (large) | 3.7V | 20,000 mAh | 74 Wh |
| Laptop Battery | 11.1V | 4,000–6,000 mAh | 44.4–66.6 Wh |
| Car Battery (12V) | 12V | 45,000–75,000 mAh | 540–900 Wh |
Wh vs mAh: What's the Difference?
| Property | Wh (Watt-hours) | mAh (Milliamp-hours) |
|---|---|---|
| Measures | Energy | Electric charge |
| Includes voltage? | Yes | No |
| Comparable across voltages? | Yes | No |
| Used by | Airlines, regulations, engineers | Consumer electronics marketing |
| Better for comparing batteries? | Yes — apples-to-apples | Only at same voltage |
Wh to mAh Examples
Related Converters
- Convert mAh to Wh — reverse conversion
- Watts / Amps / Volts Calculator
- Convert Amps to Milliamps
- Convert Milliamps to Amps
- Frequency to Wavelength — photon energy relationship for RF and EM spectrum
Formula: mAh = Wh × 1,000 / V. Results assume nominal battery voltage.
