mWh to mAh Calculator
Convert milliwatt-hours to milliamp-hours for laptop, phone and power bank batteries at any voltage.
Quick answer
To convert mWh to mAh, divide the milliwatt-hours by the nominal voltage. mAh = mWh ÷ V. A laptop battery rated 57,000 mWh at 11.4 V holds 57,000 ÷ 11.4 = 5,000 mAh. A phone battery of 19,250 mWh at 3.85 V is also 5,000 mAh, even though it stores only a third of the energy.
How to use the mWh to mAh calculator
- Enter the energy in mWh. Type the milliwatt-hour figure from the battery label, spec sheet or Windows battery report, such as 19,250 mWh for a phone or 57,000 mWh for a laptop. If you only have watt-hours, multiply by 1,000 first.
- Enter the nominal voltage. Use the voltage printed next to the mWh rating: 3.7 V or 3.85 V for one lithium-ion cell, 7.4 V or 7.7 V for two cells in series, and 11.1 V to 11.55 V or 14.8 V to 15.4 V for three and four cell laptop packs.
- Read the charge in mAh. The large number is the capacity in milliamp-hours. The cards repeat it in Ah, show the energy in Wh and give the mAh a 3.7 V power bank would need to hold the same energy.
mWh to mAh formula
A milliwatt-hour is a unit of energy. A milliamp-hour is a unit of electric charge. Energy is charge multiplied by voltage, so dividing energy by voltage gives charge back. Because both units carry the same “milli” prefix, no factor of 1,000 is needed.
Where:
- mAh is the charge capacity in milliamp-hours.
- mWh is the stored energy in milliwatt-hours. 1,000 mWh = 1 Wh.
- V is the nominal voltage of the cell or pack.
- Ah and Wh are the same values in amp-hours and watt-hours.
Working the other way, from charge to energy, is covered by the mAh to mWh calculator.
Worked examples
Example 1: Windows laptop battery report
Running powercfg /batteryreport on a Windows laptop produces a page that lists design capacity in mWh, the unit Windows itself uses (Microsoft documents the design capacity property in milliwatt-hours). Suppose the report shows 57,000 mWh and the battery label says 11.4 V, a three cell pack.
The same report shows full charge capacity, also in mWh. If that reads 48,000 mWh, the pack now holds 48,000 ÷ 11.4 = 4,211 mAh, or 84% of its design capacity. Comparing the two mWh figures gives the same percentage, so wear checks do not need the conversion. Replacement batteries are often sold by mAh, though, so this is how you match them.
Example 2: phone battery listed in mWh
Some phone teardown sheets and regulatory labels give the energy as 19,250 mWh (19.25 Wh) with a 3.85 V nominal voltage.
That matches the 5,000 mAh figure on the box. Phones with high voltage cells use 3.85 V or 3.87 V, so dividing by 3.7 V would overstate the capacity at about 5,203 mAh.
Example 3: power bank label
A power bank lists 74,000 mWh (74 Wh) at 3.7 V on the case.
This is the classic 20,000 mAh travel bank. At 74 Wh it sits under the 100 Wh airline limit, which you can check for any size with the Wh to mAh calculator.
mWh to mAh conversion table
Values in mAh, calculated as mWh ÷ V and rounded to the nearest whole number. Pick the column that matches your battery’s nominal voltage.
| Energy (mWh) | 3.7 V | 3.85 V | 7.4 V | 11.1 V | 11.4 V | 15.4 V |
|---|---|---|---|---|---|---|
| 5,000 | 1,351 | 1,299 | 676 | 450 | 439 | 325 |
| 10,000 | 2,703 | 2,597 | 1,351 | 901 | 877 | 649 |
| 19,250 | 5,203 | 5,000 | 2,601 | 1,734 | 1,689 | 1,250 |
| 37,000 | 10,000 | 9,610 | 5,000 | 3,333 | 3,246 | 2,403 |
| 50,000 | 13,514 | 12,987 | 6,757 | 4,505 | 4,386 | 3,247 |
| 57,000 | 15,405 | 14,805 | 7,703 | 5,135 | 5,000 | 3,701 |
| 74,000 | 20,000 | 19,221 | 10,000 | 6,667 | 6,491 | 4,805 |
| 99,000 | 26,757 | 25,714 | 13,378 | 8,919 | 8,684 | 6,429 |
Read across any row and the mAh falls as the voltage rises. A 15.4 V laptop pack needs only 6,429 mAh to store the same 99 Wh that a 3.7 V power bank needs 26,757 mAh for.
What affects the result
The voltage you divide by
The answer is only as good as the voltage. Lithium-ion cells are rated at 3.6 V, 3.7 V, 3.8 V or 3.85 V depending on chemistry, and LiFePO4 cells at 3.2 V. Packs multiply that by the number of cells in series. Always use the nominal figure printed on the battery, not the charging voltage (4.2 V per cell) or the 5 V USB output.
Design capacity versus full charge capacity
Battery reports give two mWh numbers. Design capacity is what the pack held when new. Full charge capacity is what it holds today. Convert the full charge figure when you want the real mAh left in an aging battery, and the design figure when you are matching a replacement.
Rounded label values
Manufacturers often round. A label of 57 Wh might be 56,900 mWh or 57,200 mWh internally, and 11.4 V might really be 11.43 V. Expect your result to land within one or two percent of the mAh printed elsewhere, not exactly on it.
Usable versus rated energy
mWh and mAh both describe the rated capacity at the nominal voltage. The energy you actually get depends on load, temperature and conversion losses. To turn capacity into hours of use, run the numbers through the battery life calculator.
Frequently asked questions
How many mAh is 1,000 mWh?
At 3.7 V, 1,000 mWh is about 270 mAh. At 3.85 V it is about 260 mAh, and at 7.4 V about 135 mAh. There is no single answer because mWh measures energy and mAh measures charge. Divide the mWh by the nominal voltage of your battery to get the right figure.
Why does Windows show battery capacity in mWh instead of mAh?
Windows reports energy because it is the fairest way to compare batteries of different voltages. A 3 cell and a 4 cell laptop pack can have the same mAh but very different energy. mWh also maps directly to runtime: divide it by the laptop’s power draw in milliwatts to estimate hours of use.
Do I need to divide by 1,000 when converting mWh to mAh?
No. Both units share the milli prefix, so they cancel. mAh = mWh ÷ V is complete. You only divide by 1,000 when moving between milli and base units, for example from mAh to Ah, or from mWh to Wh before using a formula written in amp-hours and watt-hours.
Which voltage should I use for a laptop battery?
Use the nominal voltage on the battery label. Three cell packs are usually 10.8 V, 11.1 V, 11.4 V or 11.55 V, and four cell packs 14.4 V to 15.4 V. Do not use the charger’s 19 V or 20 V USB-C rating, which would understate the mAh by roughly 40%.
Is a higher mAh battery always bigger?
Only when the voltage is the same. A 5,000 mAh phone battery at 3.85 V stores 19.25 Wh, while a 5,000 mAh laptop pack at 11.4 V stores 57 Wh, almost three times as much. Compare batteries in mWh or Wh when their voltages differ, and use mAh only within the same voltage class.