20,000 mAh to Wh
20,000 mAh is 74 Wh when the capacity rating is specified at 3.7 V. At 3.85 V, it is 77 Wh. Use the voltage printed beside the capacity on your label.
20,000 mAh at 3.7 volts equals 74 Wh.
20,000 mAh at 3.7 V
Nominal stored energy
20,000 ÷ 1,000 × 3.7 = 74 Wh
- mAh
- 20,000
- Ah
- 20
- Wh
- 74
- kWh
- 0.074
These values describe the same battery rating at 3.7 V. Results are rounded for display; reversing uses full precision.
A 10,000 mAh rating at 3.7 V is 37 Wh. At 7.4 V, the same charge capacity is 74 Wh. Check the battery label before changing the voltage.
Compare two battery labelsDifferent voltages? Compare watt-hours, not just mAh.
Understand the conversion
Which voltage belongs to a 20,000 mAh rating?
A power bank can show several voltages on its label. The voltage used to rate its internal battery capacity may differ from the voltage delivered at a USB port. Use the voltage associated with the 20,000 mAh rating.
For a 20,000 mAh rating at 3.7 V, the calculation is 20 Ah × 3.7 V = 74 Wh. Dividing that by 5 V gives 14.8 Ah, or 14,800 mAh, before conversion losses. It does not mean the power bank will deliver 20,000 mAh at every output voltage.
A 10,000 mAh rating at the same 3.7 V is 37 Wh, half the nominal energy. If the two labels use different voltages, compare their Wh ratings instead of comparing mAh alone.
Formula and worked example
Wh = 20,000 × V ÷ 1,000
At 3.7 V: Wh = 20 × 3.7 = 74
20,000 mAh × 3.7 V ÷ 1,000 = 74 Wh = 0.074 kWh.
Unit reference: NIST conversion factors lists ampere-hours under electric charge and watt-hours under energy. The battery calculations here use nominal label voltage.
20,000 mAh at different rating voltages
Each row describes a capacity rating at that voltage, not a selectable output mode on the same power bank. This reference table stays fixed while you edit the calculator.
| mAh | Nominal voltage | Wh |
|---|---|---|
| 20,000 | 3.2 V | 64 |
| 20,000 | 3.7 V | 74 |
| 20,000 | 3.85 V | 77 |
| 20,000 | 7.4 V | 148 |
| 20,000 | 12 V | 240 |
Common questions
Is 20,000 mAh always 74 Wh?
No. It is 74 Wh at 3.7 V. A 20,000 mAh rating at 3.85 V is 77 Wh, and at 7.4 V it is 148 Wh. The capacity and voltage must describe the same battery rating.
Should I enter the USB output voltage?
Only if the capacity rating is explicitly specified at that output voltage. Otherwise, use the nominal voltage associated with the internal battery capacity. Check the label or datasheet when the rating is unclear.
How many phone recharges is 74 Wh?
That needs the phone battery's energy, the power bank's usable energy, and charging losses. This converter gives nominal energy and does not predict a recharge count.