Battery Size Table
| Size | IEC (alkaline) | ANSI | Voltage | Diameter × height (mm) | Typical capacity* |
|---|---|---|---|---|---|
| AAAA | LR8D425 | 25A | 1.5 V | 8.3 × 42.5 | 400-600 mAh (NiMH) |
| AAA | LR03 | 24A | 1.5 V | 10.5 × 44.5 | 1,200 mAh |
| AA | LR6 | 15A | 1.5 V | 14.5 × 50.5 | 2,700 mAh |
| C | LR14 | 14A | 1.5 V | 26.2 × 50.0 | 8,000 mAh |
| Sub-C | HR22C429 (NiMH) | — | 1.2 V | 22.2 × 42.9 | 1,800-5,000 mAh (NiMH) |
| D | LR20 | 13A | 1.5 V | 34.2 × 61.5 | 12,000 mAh |
| F | LR25 | 60 | 1.5 V | 33 × 91 | 26,000 mAh |
| N | LR1 | 910A | 1.5 V | 12 × 30.2 | 800-1,000 mAh |
| A21 | 4LR932 | 1811A | 6 V | 10.3 × 16.0 | 55 mAh |
| A23 | 8LR932 | 1811A | 12 V | 10.3 × 28.5 | 55 mAh |
| A27 | 8LR732 | — | 12 V | 8.0 × 28.2 | 22 mAh |
| 9V (PP3) | 6LR61 | 1604A | 9 V | 26.5 × 48.5 × 17.5 | 565 mAh |
Household batteries live in a double naming system that refuses to die: the everyday letters everyone says (AA, AAA, C, D) and the codes printed on the wrapper that actually mean something (LR6, LR03, 6LR61). The letter names are the nickname; the IEC code is the specification - and the code is worth learning because it decodes itself. The first letter names the chemistry: L is alkaline, R alone is the old carbon-zinc, F is lithium iron disulfide, H is nickel-metal hydride. The R in the middle means round cell. The number is the size. So LR6 reads as: alkaline, round, size 6 - which is the cell everyone calls AA. Once you can read that, the drawer of mystery batteries becomes an open book, and the chart below is the translation layer for every common size.
The second surprise in the table is the ANSI number column, because it runs backwards: the bigger cell gets the smaller number. D is ANSI 13, C is 14, AA is 15, AAA is 24, and the skinny AAAA is 25. The same backwards habit shows up in drill gauges and wire sizes - anything numbered before calculators inherited counting schemes that made sense at the time and confuse everyone now. The dimensions and capacities, though, are refreshingly honest: from AAAA at 8.3 millimeters up to D at 34.2, each step up in diameter buys real runtime, and every chemistry in the same size shares the same 1.5 volts - the size changes how long the battery lasts, not how hard it pushes.
How to use
- Identify first: read the IEC code on the wrapper (or measure diameter and height with the millimeter column) and match it in the chart - the IEC and ANSI columns are the authoritative identity when a letter nickname is worn off or regional.
- Match voltage before anything else: every cylindrical cell here is 1.5 volts (or 1.2 for rechargeable NiMH), but the stacked 12-volt A23/A27 and 9-volt PP3 are different animals - never substitute across a voltage boundary regardless of physical fit.
- When a device takes multiple cells, replace the whole set at once with the same chemistry: an old cell in a series string drags the others and invites leakage - and if the device tolerates NiMH, plan on 1.2 volts per cell instead of 1.5.
Frequently asked questions
What is the actual difference between AA and AAA batteries?
Physics, not chemistry: an AA cell is 14.5 by 50.5 millimeters, an AAA is 10.5 by 44.5 - same voltage, same nominal 1.5 volts, but the AA carries roughly 2,700 milliamp-hours against the AAA at about 1,200. The AA holds a little over twice the fuel in a can about forty percent fatter. That is the entire difference, and it is why the choice in a device is about the volume the designer was willing to spend: two AA cells in series run anything two AAAs would, but roughly twice as long before the swap. The chemistry column matters more than the letter when you care about runtime - an alkaline AA at 2,700 milliamp-hours outruns a cheap carbon-zinc AA at 1,100 by nearly three times, so the wrapper word (alkaline versus heavy duty) is often worth more than the size upgrade.
Why is a 9-volt battery 9 volts when AA cells are 1.5?
Because it is not one cell - it is a stack. The IEC name gives it away: 6LR61 means six size-61 cells wired in series inside the rectangular case, and six times 1.5 volts lands on 9. The official dimensions are 48.5 by 26.5 by 17.5 millimeters, and the six cells packed inside are each about the size of an AAAA - which is exactly why a 9-volt holds a modest 565 milliamp-hours at best: the fuel tank is full of partitions. The same stacking trick explains the little 12-volt A23 (8LR932: eight button-size LR932 cells in a tube) and the A27 (8LR732). Series stacking buys voltage at the cost of capacity and interior space, which is why the 9-volt survives only where the 9 volts is non-negotiable - smoke alarms and multimeters - and lost everywhere else to packs of AAs.
What do the letters and numbers in an IEC battery code mean?
The code is a spec sheet in five characters. Leading letter: chemistry - L is alkaline, plain R (no leading letter) is the old zinc-carbon, F is lithium iron disulfide, H is nickel-metal hydride, K is nickel-cadmium, P appears for zinc-air variants. The middle R means round (cylindrical). The trailing number is the size code: 6 for AA, 03 for AAA, 14 for C, 20 for D, 1 for N, 8D425 for AAAA. So LR03 is an alkaline AAA while HR03 is a NiMH AAA and FR03 is a lithium AAA - identical shape, different guts, and the distinction matters in high-drain devices where lithium or NiMH holds voltage far better under load than zinc-carbon ever did. Stacked rectangular types prefix the cell count: 6LR61 is the 9-volt, 4LR25Y the 6-volt lantern. Once you know the grammar you can shop by code instead of by brand table.
Can I use 1.2-volt rechargeables where the device asks for 1.5-volt batteries?
Usually yes, with one honest caveat. A fresh alkaline cell starts near 1.6 volts and sags under load almost immediately, spending most of its life between 1.3 and 1.2 volts - which is almost exactly where a NiMH cell lives for its whole discharge. That is why most devices designed around alkalines run fine on NiMH: the curves overlap for most of the runtime. The exceptions are the devices that measure voltage as a fuel gauge - some smoke alarms and cheap remotes declare a cell dead at a fixed threshold, and a 1.2-volt NiMH trips that line early even with a full charge. The second caveat is self-discharge chemistry: classic NiMH cells drain on the shelf, so for low-drain sit-around devices (clocks, remotes) lithium primaries or alkalines hold charge longer, while high-drain users (camera flashes, toys, keyboards) get the money back fast with low-self-discharge NiMH packs. The chart capacity column shows the gap directly: 1.5-volt alkaline figures versus the 1.2-volt NiMH lines.