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Ah to Wh Calculator

Convert amp-hours to watt-hours (and back) at any battery voltage — for solar batteries, e-bikes, power stations and power banks.

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Direction

Capacity

Battery voltage

Use the nominal voltage on the label: 12.8 V for a “12 V” LiFePO₄ battery, 3.6–3.7 V for a lithium-ion cell or power bank.

Energy

— Wh

—

Watt-hours—

Kilowatt-hours—

Amp-hours—

Milliamp-hours—

Nominal (rated) energy. Usable energy is lower: about 80–100% for lithium, about 50% for lead-acid.

Quick answer

Watt-hours = amp-hours × volts, and amp-hours = watt-hours ÷ volts.

100 Ah at 12 V = 1,200 Wh; a 100 Ah “12 V” LiFePO₄ (12.8 V nominal) = 1,280 Wh
20 Ah e-bike battery at 36 V = 720 Wh
10,000 mAh power bank at 3.7 V = 10 Ah × 3.7 = 37 Wh
5,000 Wh at 48 V = 104 Ah

Need kilowatt-hours for a solar bank? Use the Ah to kWh calculator.

How this conversion works

Wh = Ah × V · Ah = Wh ÷ V · kWh = Wh ÷ 1,000 · mAh = Ah × 1,000.
Use the battery’s nominal voltage.

Ah to Wh: why voltage matters

Amp-hours tell you how much charge a battery holds; watt-hours tell you how much energy. The link between them is voltage. Two batteries rated 100 Ah store very different energy at 12 V and 48 V, so watt-hours are the fair way to compare batteries, power stations and power banks — and the number airlines, battery runtime calculators and solar sizing tools ask for.

Use the nominal voltage

A “12 V” LiFePO₄ battery has four cells at 3.2 V, so its nominal voltage is 12.8 V; a “48 V” rack is usually 51.2 V. Lithium-ion cells in phones, laptops and power banks are 3.6–3.85 V. Using the true nominal voltage gives the watt-hours printed on the datasheet.

Ah to Wh conversion chart

Capacity	12 V	12.8 V	24 V	25.6 V	48 V	51.2 V
5 Ah	60 Wh	64 Wh	120 Wh	128 Wh	240 Wh	256 Wh
7 Ah	84 Wh	90 Wh	168 Wh	179 Wh	336 Wh	358 Wh
10 Ah	120 Wh	128 Wh	240 Wh	256 Wh	480 Wh	512 Wh
20 Ah	240 Wh	256 Wh	480 Wh	512 Wh	960 Wh	1,024 Wh
35 Ah	420 Wh	448 Wh	840 Wh	896 Wh	1,680 Wh	1,792 Wh
50 Ah	600 Wh	640 Wh	1,200 Wh	1,280 Wh	2,400 Wh	2,560 Wh
100 Ah	1,200 Wh	1,280 Wh	2,400 Wh	2,560 Wh	4,800 Wh	5,120 Wh
150 Ah	1,800 Wh	1,920 Wh	3,600 Wh	3,840 Wh	7,200 Wh	7,680 Wh
200 Ah	2,400 Wh	2,560 Wh	4,800 Wh	5,120 Wh	9,600 Wh	10,240 Wh
280 Ah	3,360 Wh	3,584 Wh	6,720 Wh	7,168 Wh	13,440 Wh	14,336 Wh
300 Ah	3,600 Wh	3,840 Wh	7,200 Wh	7,680 Wh	14,400 Wh	15,360 Wh

Common batteries in watt-hours

Battery	Rating	Voltage	Energy
Phone / power bank	10,000 mAh	3.7 V	37 Wh
Power bank	20,000 mAh	3.7 V	74 Wh
Laptop battery	4,500 mAh	11.55 V	52 Wh
Drone battery	5,000 mAh	15.4 V	77 Wh
E-bike battery	14 Ah	36 V	504 Wh
E-bike battery	17.5 Ah	48 V	840 Wh
Golf-cart / trolling	105 Ah	12 V	1,260 Wh
Home battery rack	100 Ah	51.2 V	5,120 Wh

Frequently asked questions

How do I convert Ah to Wh?

Multiply amp-hours by the battery voltage. 100 Ah × 12 V = 1,200 Wh. To go back, divide watt-hours by the voltage.

How many watt-hours is a 100Ah battery?

1,200 Wh at 12 V, 1,280 Wh for a 12.8 V LiFePO₄, 2,400 Wh at 24 V and 4,800 Wh at 48 V (5,120 Wh at 51.2 V).

How do I convert mAh to Wh?

Divide mAh by 1,000 to get Ah, then multiply by the voltage. A 20,000 mAh power bank at 3.7 V holds 20 × 3.7 = 74 Wh.

Is Wh or Ah a better way to compare batteries?

Watt-hours, because they include voltage. Amp-hours only compare fairly between batteries of the same voltage.

How many Ah is 1,000 Wh?

It depends on voltage: 83.3 Ah at 12 V, 78.1 Ah at 12.8 V, 41.7 Ah at 24 V and 20.8 Ah at 48 V.

Electrical unit converters

Learn more

DIYSizing an off-grid battery bankDays of autonomy, depth of discharge and real capacity.FundamentalsIs a solar battery worth it?When storage pays off — and when it doesn't.FundamentalsWhat size inverter do I need?Matching inverter capacity to your array, and the DC-to-AC ratio.

Sources & standards

Watt-hours are amp-hours times volts, a direct consequence of SI unit definitions. The same method is what aviation regulators use to rate lithium batteries.

NIST Special Publication 811 — Guide for the Use of the International System of Units (SI) — National Institute of Standards and Technology
Defines the watt, watt-hour, ampere and the conversion factors used on this page.
PackSafe — Lithium Batteries — Federal Aviation Administration
Source of the 100 Wh and 101–160 Wh carry-on limits for spare lithium-ion batteries and power banks, and the Wh = V × Ah method.