Two naming habits
Household cylinders are usually sold under ANSI / common size letters: AAAA, AAA, AA, C, D, plus the rectangular 9V.
Manuals and many EU/Asia packs often print the IEC form instead — for example LR6 or R6 for AA, LR03 or R03 for AAA. Same size family, different label style — not a different battery by itself.
This is not the same pattern as CR / LR / SR coin cells. Those two-letter prefixes start with a chemistry letter plus R for round. AA / AAA / AAAA are size names; chemistry (alkaline, NiMH, lithium primary) is chosen separately.
Size ladder (smallest → largest)
AAAA — slim specialty cylinder (IEC LR8D425 / R8D425). Common in some replaceable styluses such as Microsoft Surface Pen generations that still take a cell.
AAA — smaller everyday cylinder (IEC LR03 / R03; also UM-4 / MN2400 on some packs).
AA — the everyday workhorse (IEC LR6; also AM3 / MN1500). About 14.5 × 50.5 mm in our ontology.
C and D — larger flashlight / radio sizes in the same ANSI ladder. We do not currently publish dedicated C / D catalogue pages; identify them from the device or pack label.
Letter count is not a math formula — “more A’s” just means a different standard size step, not “A times four”.
Common IEC / pack crosswalk
AA ↔ LR6 (alkaline IEC) / R6 (zinc-carbon IEC form). Brand packs may say MN1500 or AM3.
AAA ↔ LR03 / R03. Brand packs may say MN2400, UM-4, or AM4.
AAAA ↔ LR8D425 / R8D425.
9V ↔ 6LR61 (alkaline stack) / PP3 / MN1604. Not a single “R” cylinder — a rectangular multi-cell pack.
N ↔ LR1 / E90 / MN9100 / AM5 — a short 1.5V specialty cylinder, smaller than AAA. Not an AA step.
Chemistry is separate from size
An “AA” tray can be filled with alkaline, NiMH rechargeable, or lithium primary (e.g. L91) — only when the device allows that chemistry.
Nest Protect and some cameras name lithium AA specifically. Bose remotes and many calculators name alkaline AAA. Match the device page, not the size letter alone.
See NiMH vs alkaline and the rechargeable AA / AAA guide when the maker allows rechargeables.
Not the AA family — A23 and A27
A23 (23A / MN21 / 8LR932) and A27 (27A / MN27) are 12-volt miniature alkaline cylinders for remotes and keypads.
They are not AA / AAA / AAAA sizes and not phone batteries. Match A23 or A27 exactly — they are not interchangeable by voltage alone.
Quick takeaway
Read the size letter (or IEC code) first — AA is not AAA is not AAAA. Then confirm chemistry on the device page. For coin and button cells, use the CR vs LR vs SR guide instead.