How do I compare batteries rated at different voltages?

Convert both to watt-hours by multiplying Ah by voltage. A 100Ah 12V battery and a 200Ah 6V battery both store 1,200Wh — identical total energy despite very different Ah numbers. Always use Wh as the common unit when comparing batteries across voltages. Two 6V 200Ah batteries wired in series produce 12V at 200Ah (2,400Wh total), which is why off-grid systems often pair 6V golf cart batteries for higher capacity.

Why do power banks list mAh but solar batteries list Wh?

Power banks traditionally listed mAh because all USB devices used a standard 5V, making mAh a useful comparison within that ecosystem. Solar batteries list Wh because they operate at various voltages (12V, 24V, 48V) and Wh allows direct comparison. With USB-C PD delivering 5V, 9V, 15V, or 20V, mAh is becoming misleading even for power banks. Always check Wh for an accurate energy comparison.

How do I convert kWh on my electric bill to Ah?

First convert kWh to Wh by multiplying by 1,000. Then divide by the system voltage. If you used 30kWh last month and want to know the equivalent Ah at 120V (grid voltage): 30,000Wh / 120V = 250Ah. This does not directly apply to battery sizing because grid power comes at constant voltage while batteries have variable voltage during discharge, but it gives you a sense of scale. For solar system planning, our solar watts-to-amps calculator handles the same conversion at panel voltages.

Watt Hours to Amp Hours Calc — Free

4 min read

Watt-hours and amp-hours measure different things: Wh measures total energy, Ah measures charge capacity at a given voltage. Converting between them is simple division, but getting the voltage wrong gives you a wildly incorrect answer. This calculator handles the math cleanly.

Watt hours to amp hours conversion dividing energy by voltage for battery sizing.

How to Convert Wh to Ah (Step by Step)

Identify the watt-hour rating. Find the Wh value on the battery label, product spec sheet, or manufacturer website. Power banks, laptop batteries, and some solar batteries list Wh prominently. If only mWh is listed, divide by 1,000 to get Wh.
Identify the nominal voltage. Common voltages: 3.7V (lithium-ion cells and power banks), 12V (car and marine batteries), 12.8V (LiFePO4 "12V"), 24V (larger systems), 48V (off-grid solar). Using the wrong voltage gives the wrong amp-hour number.
Divide. Amp-hours = Watt-hours / Voltage. A 1,000Wh battery at 12V = 83.3Ah. That same 1,000Wh at 48V = only 20.8Ah — but it stores the same energy.
Verify units. If your source lists kWh (kilowatt-hours), multiply by 1,000 to get Wh first. A 5kWh home battery = 5,000Wh.

Wh-to-Ah conversion formula with arrows linking watt hours, voltage, and amp hours. — The same 500 Wh battery is 41.7 Ah at 12V but only 10.4 Ah at 48V — always specify voltage when comparing battery capacity.

Wh to Ah Quick Reference Table

Wh	At 3.7V (Ah)	At 12V (Ah)	At 24V (Ah)	At 48V (Ah)
37 Wh	10 Ah	3.1 Ah	1.5 Ah	0.8 Ah
74 Wh	20 Ah	6.2 Ah	3.1 Ah	1.5 Ah
500 Wh	135 Ah	41.7 Ah	20.8 Ah	10.4 Ah
1,000 Wh	270 Ah	83.3 Ah	41.7 Ah	20.8 Ah
2,400 Wh	649 Ah	200 Ah	100 Ah	50 Ah
5,000 Wh	1,351 Ah	416.7 Ah	208.3 Ah	104.2 Ah

Remember: higher voltage systems use fewer amp-hours for the same stored energy. This means thinner cables, smaller fuses, and lower current — one of the main reasons large off-grid systems run at 48V instead of 12V.

Worked Examples

Comparing Two Solar Batteries Listed in Different Units

Context

Battery A: 1,200 Wh at 12V. Battery B: 60Ah at 24V. Which stores more energy and which is better for a 12V system?

Calculation

Battery A: 1,200 Wh / 12V = 100 Ah

Battery B: 60 Ah x 24V = 1,440 Wh → at 12V equivalent: 1,440 / 12 = 120 Ah

Interpretation

Battery B stores 20% more energy (1,440 vs 1,200 Wh). But it is a 24V battery — you cannot use it in a 12V system without a converter, which adds cost and efficiency losses.

Takeaway

Always match battery voltage to your system voltage. For runtime comparisons at your system voltage, use our battery runtime calculator.

How Many Ah in a Drone Battery?

Context

Your drone battery is rated 5,200 mAh at 22.2V (6S LiPo). You want to know the watt-hours and amp-hours for comparison with a spare rated differently.

Calculation

Wh = 5,200 mAh x 22.2V / 1,000 = 115.4 Wh

Ah = 5,200 / 1,000 = 5.2 Ah

Interpretation

115 Wh is similar to a large laptop battery. The high voltage (22.2V) means the Ah number seems low, but the total energy is substantial — enough for 20-35 minutes of flight depending on the drone. Get a precise estimate with the drone battery flight time calculator.

Takeaway

For more on converting between mAh, Ah, and Wh, see our reserve capacity to Ah converter for lead-acid-specific conversions.

Frequently Asked Questions

Glossary

Watt-Hours

A measure of total energy that combines voltage and amp-hours. Wh = Ah x V. This is the only unit that allows direct comparison between batteries of different voltages — a 50Ah 24V battery (1,200 Wh) equals a 100Ah 12V battery (1,200 Wh).

Kilowatt-Hours

One thousand watt-hours. Used for larger batteries like EV packs and home storage systems. A Tesla Powerwall holds 13.5 kWh (13,500 Wh). Your electric utility bills you in kWh.

Voltage-Capacity Relationship

At constant energy, higher voltage means lower amp-hours. A 48V 25Ah battery stores the same 1,200 Wh as a 12V 100Ah battery. Higher voltage systems use thinner wire (lower current) but require more cells in series.

Sizing a solar battery bank? The <a href="/solar/solar-battery-bank-size-calculator">solar battery bank size calculator</a> uses Wh to match storage to daily generation.

Wh to Ah conversion is the most fundamental battery math skill. Whenever you see a battery rated in one unit and need the other, divide by voltage. Get comfortable with this conversion and every other battery calculation becomes straightforward. Laptop batteries are commonly rated in Wh — convert to Ah, then estimate your real-world runtime with our laptop battery runtime calculator.

Last updated: March 16, 2026

Written and maintained by Dan Dadovic, Commercial Director at Ezoic Inc. & PhD Candidate in Information Sciences. He works professionally as Commercial Director at Ezoic Inc., leading revenue strategy across digital publishing.

Disclaimer: Calculator results are estimates based on theoretical formulas. Actual performance varies with temperature, battery age, load patterns, and equipment condition. For critical electrical work, consult a licensed electrician.