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.
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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
| 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
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.
Why devices offer both
A manufacturer choosing AAA is usually buying slimness — a remote you hold in one hand, a slim keyboard. Choosing AA buys runtime and the ability to sustain more current. The same product line often ships both, with the AAA version quoting noticeably shorter battery life.
Mixing sizes in one device
Some equipment takes four AA or four AAA depending on a tray insert. Never mix the two in one compartment even where an adapter makes it physically possible: the cells discharge at different rates, and the weaker one can be driven into reverse by the stronger, which is how alkaline cells leak.
Rechargeable versions of both
NiMH exists in both sizes at 1.2 V and the same size relationship holds, roughly 2000 mAh for an AA against 800 for an AAA. If you are converting a household to rechargeables, the AA devices repay it faster simply because they tend to be the hungrier ones.
Can I use an AAA instead of an 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.
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.
AA vs AAA: common questions
Is the AAA a direct replacement for the AA?
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.
What is the difference between the AA and the 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. In short: same voltage, entirely different size.
Are the AA and the AAA the same size?
No. The AA is 14.5 × 50.5 mm and the AAA is 10.5 × 44.5 mm.
Which lasts longer, the AA or the AAA?
The AA. It is rated at 1800–2900 mAh against 850–1200 mAh for the AAA — roughly 2.3× the capacity, though real runtime depends on how much current your device draws.
Background reading
The wider questions behind these two codes.
Lithium for cold, weight and high drain; alkaline for everything else
NiMH for anything you replace often, alkaline for anything you forget about
Switch anything you replace more than twice a year
Lithium for standby and extremes, NiMH for anything used often