Electrical & Lighting · Conversion · Free

mAh to Wh Calculator

Convert electric charge in milliamp-hours (mAh) to energy in watt-hours (Wh). Enter the charge and the voltage, and press Calculate — the energy is E(Wh) = Q(mAh) × V(V) / 1000. Everything runs locally in your browser.

STEP 1

Enter the charge in mAh

Type the battery or power-bank capacity in milliamp-hours (mAh) — for example 3000 for a typical phone battery or 5000 for a large one.

STEP 2

Enter the voltage in V

Type the nominal voltage in volts (V): 3.7 V for a single lithium-ion cell, 5 V for USB, 12 V for a lead-acid battery. Zero is valid here because the formula only divides by the constant 1000.

STEP 3

Press Calculate, read Wh

The energy appears in watt-hours (Wh). Press Reset at any time to clear the inputs and the result and start over.

mAh to Wh formula

How do I convert mAh to Wh?: The energy E in watt-hours is equal to the electric charge Q in milliamp-hours times the voltage V in volts, divided by 1000: E(Wh) = Q(mAh) × V(V) / 1000. So watt-hours is milliamp-hours times volts divided by 1000.
Example: how many Wh is 3000 mAh at 5 V?: E = 3000 mAh × 5 V / 1000 = 15 Wh. At the 3.7 V nominal voltage of a single lithium-ion cell the same 3000 mAh pack stores 3000 × 3.7 / 1000 = 11.1 Wh.
Why does the voltage matter?: mAh measures charge, not energy. The same 5000 mAh cell stores 18.5 Wh at 3.7 V but only 12.5 Wh if it discharges down to an average of 2.5 V — energy is charge pushed through a potential, so Wh scales linearly with voltage.
Which voltage should I enter for a battery pack?: Use the pack nominal voltage: about 3.7 V per lithium-ion cell in series (11.1 V for a 3S pack), 2 V per lead-acid cell (12 V for a car battery), or 5 V for USB output ratings. Manufacturer capacity labels are usually quoted at the nominal voltage.
Is a power bank's mAh rating directly comparable between brands?: Only at the same cell voltage. Airlines cap carry-on batteries at 100 Wh (with airline approval up to 160 Wh), and Wh — not mAh — is the number that matters, which is exactly why converting at the cell's nominal voltage (usually 3.7 V) is the honest comparison.

Privacy: every calculation runs in your browser tab — no value you type is sent anywhere. Results are ideal DC conversions; real battery energy differs with discharge rate, temperature, and cutoff voltage.