AA and AAA batteries have the same voltage: 1.5 volts for alkaline and lithium, and 1.2 volts for rechargeable NiMH. The difference is size and capacity. An AA is about 14.5 mm wide and 50.5 mm long; an AAA is thinner and shorter, at about 10.5 mm by 44.5 mm. Because an AA holds roughly twice as much material, it lasts longer in the same device.
This guide compares AA and AAA batteries side by side, using the manufacturer’s own data sheets (Energizer) and the international battery codes. It covers size, weight, voltage, capacity, the codes printed on batteries (LR6, LR03 and more), and which one your device needs.
| AA | AAA | |
|---|---|---|
| Diameter | 13.5-14.5 mm (about 0.57 in) | 9.5-10.5 mm (about 0.41 in) |
| Length | 49.5-50.5 mm (about 1.99 in) | 43.3-44.5 mm (about 1.75 in) |
| Volume | 8.1 cm³ | 3.8 cm³ |
| Weight (alkaline) | 23 g (0.8 oz) | 11.5 g (0.4 oz) |
| Voltage (alkaline / lithium) | 1.5 V | 1.5 V |
| Voltage (rechargeable NiMH) | 1.2 V | 1.2 V |
| Rechargeable capacity (example) | 2,300 mAh | 800 mAh |
| IEC code (alkaline) | LR6 | LR03 |
| ANSI code (alkaline) | 15A | 24A |
AA vs AAA size
An AA battery is up to 14.5 mm (0.57 in) across and 50.5 mm (1.99 in) long. An AAA is up to 10.5 mm (0.41 in) across and 44.5 mm (1.75 in) long. So an AAA is only about 6 mm shorter, but it is much thinner. That matters most for volume: an AA takes up 8.1 cm³, more than twice the 3.8 cm³ of an AAA.
These sizes are industry standards, so any brand’s AA fits a device made for AA, and the same goes for AAA. You can’t swap one size for the other: an AAA is too thin and too short for an AA slot, and an AA won’t fit an AAA slot.
Do AA and AAA batteries have the same voltage?
Yes. Voltage depends on the battery’s chemistry, not its size:
- Alkaline: 1.5 V for both AA and AAA
- Lithium (lithium iron disulfide): 1.5 V for both
- Rechargeable NiMH: 1.2 V for both
Many devices that take alkaline batteries also work with 1.2 V rechargeables, but check your device’s manual if you’re unsure.
Which lasts longer: AA or AAA?
An AA lasts longer, because it is bigger and holds more of the chemicals that store energy. Battery capacity is measured in milliamp-hours (mAh). For example, Energizer rates its rechargeable AA (NH15-2300) at 2,300 mAh and its rechargeable AAA (NH12-800) at 800 mAh, almost three times less.
Alkaline batteries don’t have one fixed mAh figure. Their capacity drops as the device draws more power, so data sheets show it as a curve. In general, a device that drains batteries fast (like a toy or a torch) gets much less from an alkaline battery than a low-drain device like a clock or remote.
What the codes on batteries mean
Batteries carry an international (IEC) code as well as the name AA or AAA. The letters show the chemistry, and the number shows the size:
| Chemistry | AA code | AAA code | Voltage |
|---|---|---|---|
| Alkaline | LR6 | LR03 | 1.5 V |
| Lithium (Li/FeS2) | FR6 | FR03 | 1.5 V |
| Rechargeable NiMH | HR6 | HR03 | 1.2 V |
Alkaline, lithium or rechargeable?
- Alkaline: cheap and common. Energizer lists a shelf life of 10 years and an operating range of -18°C to 55°C (0°F to 130°F). Good for remotes, clocks and other low-drain devices.
- Lithium (non-rechargeable): lighter (an AA weighs 15 g against 23 g for alkaline), with a 25-year shelf life and a wider range of -40°C to 60°C (-40°F to 140°F). Good for cameras, outdoor gear and devices left in the cold.
- Rechargeable NiMH: 1.2 V, but can be recharged many times. Good for devices you use every day, like game controllers and toys.
Which devices use AA or AAA?
Always use the size your device asks for. As a rough guide, smaller and thinner gadgets tend to use AAA, while devices that need more power or longer running time tend to use AA:
- Often AAA: TV remotes, computer mice, small torches, digital thermometers and other slim gadgets.
- Often AA: clocks, toys, game controllers, larger torches and radios.
Check the battery compartment or the manual: the size and the + and − direction are usually marked inside.
Related guides: how to test and replace smoke alarm batteries, the power bank rules on flights, and what the “milli” in mAh means in our guide to metric prefixes.
Frequently asked questions
What is the difference between AA and AAA batteries?
Size and capacity. AA batteries are bigger (about 14.5 x 50.5 mm against 10.5 x 44.5 mm) and hold more energy, so they last longer. The voltage is the same.
Can I use AAA instead of AA?
Not directly. An AAA is too small to make proper contact in an AA slot. Use the size your device is made for.
Are AA batteries more powerful than AAA?
They have the same voltage, but an AA stores more energy, so it can run a device for longer. For example, a rechargeable AA rated 2,300 mAh holds almost three times as much as an 800 mAh AAA.
What does LR6 mean on a battery?
LR6 is the international (IEC) code for an alkaline AA battery. An alkaline AAA is LR03.
Why do rechargeable batteries say 1.2 V?
Nickel-metal hydride (NiMH) chemistry has a nominal voltage of 1.2 V, a little lower than the 1.5 V of alkaline. Many devices work fine with either; check your manual.
How long do AA batteries last in storage?
Energizer lists a shelf life of 10 years at 21°C (70°F) for its alkaline AA and 25 years for its lithium AA.
Which is bigger, AA or AAA?
AA is bigger. It is about 4 mm wider and 6 mm longer than an AAA, and has more than twice the volume.
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