AA, AAA, and AAAA look almost identical on a shelf, and mixing them up is the single most common reason a "battery" fix doesn't actually fix anything. Here's how to tell them apart fast, and which devices actually use which.
Size and shape at a glance
| AA | AAA | AAAA | |
|---|---|---|---|
| Length | ~50.5mm | ~44.5mm | ~41.5mm |
| Diameter | ~14.5mm | ~10.5mm | ~8.3mm |
| Relative size | Standard, thickest | Slimmer, shorter than AA | Thinnest and shortest of the three |
The quickest way to tell them apart without a ruler: AA is the "normal" battery most people picture, AAA is the noticeably thinner one used in most TV remotes, and AAAA is the rare, pencil-thin size that only shows up in a handful of compact devices.
What actually uses AA
AA is the most common household size: TV and aircon remotes (older models), wall clocks, wireless mice and keyboards, toys, torches, and many portable radios. If a device takes "regular" batteries and you're not sure, AA is the safer first guess.
What actually uses AAA
AAA shows up in smaller or lighter devices: most modern TV remotes, compact torches, kitchen scales, some game controllers, and smaller wireless mice. It's the second most common size after AA.
What actually uses AAAA
AAAA is genuinely uncommon, and it exists specifically for devices too slim for a AAA cell. The most frequent use case by far is stylus pens, active pens for tablets like the Surface or Kobo, sonic tooth scalers, small Bluetooth headsets, and glucose or blood pressure monitors. If a stylus or slim pen-shaped device has taken its battery out and you don't recognise the size, it's very likely AAAA, not AAA.
Quick way to check what your device needs
- Check the battery compartment sticker or manual, it's almost always printed there.
- If there's an old battery still inside, compare its length against the table above.
- Stylus pens, active pens, and anything pen-shaped: try AAAA first, not AAA.
- TV remotes: most are AAA, but some older or larger remotes take AA, check before buying.
Rechargeable or disposable?
All three sizes come in both disposable alkaline and rechargeable form. If you're going through batteries often (game controllers, TV remotes in a busy household), rechargeable pays for itself faster. See our full breakdown: Rechargeable vs Disposable Batteries: Is It Worth It?
Related products
Browse the full range on our Alkaline & Heavy Duty Batteries collection.
Frequently asked questions
Can I use a AAA battery in a device that takes AA, or vice versa?
No, not directly. AA and AAA are different diameters and lengths, so a AAA cell will not make contact properly in an AA-sized compartment, and a AA cell physically will not fit into a AAA-sized one. Adapter sleeves exist for AAA-into-AA compartments but are uncommon and not something we stock.
My stylus pen says it needs AAAA but I can only find AAA locally, are they interchangeable?
No. AAAA is thinner and shorter than AAA and will not fit or make proper contact in a AAAA compartment. Double check the compartment marking, or the size of the old cell if there is one, before buying.
Why is AAAA so much harder to find than AA or AAA?
Far fewer devices use it, mainly slim pen-shaped electronics, so retailers stock much less of it. It also tends to cost more per cell than AA or AAA for the same reason.
Do AA, AAA, and AAAA all run at the same voltage?
Yes, all three are 1.5V in standard alkaline form (or 1.2V rechargeable), the difference between them is physical size and capacity, not voltage.