AA vs AAA

Both are 1.5 V alkaline cylindrical cells. At 14.5 × 50.5 mm against 10.5 × 44.5 mm, the AA holds roughly two and a half times the energy.

Quick answer

Both give 1.5 volts, so neither is the more powerful battery — the AA is simply bigger and holds about two and a half times as much, so it lasts that much longer. They are not swappable: an AAA is both thinner and shorter, and will not reach the contacts in an AA compartment. Adapter sleeves exist and do work, but they give you AAA runtime in an AA-shaped package.

Verdict:: Same voltage, entirely different size
Interchangeable:: no

Side-by-side specifications

AA compared with AAA
Specification	AA	AAA
Chemistry	Alkaline	Alkaline
Type	Cylindrical	Cylindrical
Nominal voltage	1.5 V	1.5 V
Diameter	14.5 mm	10.5 mm
Height	50.5 mm	44.5 mm
Typical capacity	1800–2900 mAh	850–1200 mAh
Rechargeable	No	No
Also sold as	LR6, MN1500, AM3, R6	LR03, MN2400, AM4, R03

Size comparison

Ø 14.5 mm · H 50.5 mm

AAA

Ø 10.5 mm · H 44.5 mm

These cells do not share a footprint, so one will not sit correctly in the other's compartment.

Size

14.5 × 50.5 mm against 10.5 × 44.5 mm. The AAA is 4 mm narrower and 6 mm shorter — too small on both axes to bridge an AA compartment's contacts.

Runtime

1800–2900 mAh against 850–1200 mAh. Roughly two and a half times the reserve, which is why a device offered in both sizes quotes very different battery life for each.

Adapter sleeves

A plastic sleeve holds an AAA in an AA bay and works, because the voltage is identical. What it cannot do is add capacity: you get the AAA's runtime and its lower current ceiling, so it suits a clock far better than a motorised toy.

Can I use a AAA instead of a AA?

Not directly. The AAA measures 10.5 × 44.5 mm against 14.5 × 50.5 mm for the AA, so it will not seat properly in the same compartment.

AA specs →AAA specs →

Check before you swap. Batteries with similar dimensions are not always interchangeable. Always verify voltage, chemistry and the requirements printed in your device manual before fitting a replacement.

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