AAA battery Size & Weight

A AAA battery is 44.5 mm long and 10.5 mm in diameter (IEC designation R03 / LR03). An alkaline AAA weighs about 11.5 grams, roughly half the weight of an AA. It is the standard cell for remotes, small torches, computer mice, and slimline devices.

This guide covers the exact AAA dimensions, why it holds much less energy than an AA despite looking similar, how it compares to an AA and a AAAA, and how it sizes up against a coin and a pen.

Quick Answer: How Big Is a AAA Battery?

A AAA cell is 44.5 mm tall and 10.5 mm across, with a small raised positive terminal included in that length. Alkaline weight is ~11.5 g; lithium AAAs are about 7.6 g and NiMH about 13 – 15 g.

AAA Battery Dimensions at a Glance

• Length: 44.5 mm max
• Diameter: 10.5 mm nominal (about 10.0 – 10.5 mm)
• Capacity: an alkaline AAA holds roughly 1,000 – 1,200 mAh, versus 2,000 – 3,000 mAh for an alkaline AA, because it has less than half the internal volume
• A 4-pack side by side is about 42 x 44.5 x 10.5 mm
• Terminal: raised button positive, flat negative

What Does a AAA Battery Look Like in Size?

A AAA is about the length of a US quarter’s diameter doubled, or roughly the length of an adult’s thumb. Its 10.5 mm diameter is close to a pencil without the paint. Four AAAs in a row span about 42 mm, a bit less than the diameter of a golf ball.

6 Everyday Comparisons for a AAA Battery

1. An AA battery (50.5 x 14.5 mm) is 6 mm longer and 4 mm wider, and about twice the weight.
2. A AAAA battery (42.5 x 8.3 mm) is 2 mm shorter and 2.2 mm narrower, used in some styluses and laser pointers.
3. A US quarter (24.26 mm) is about 55% of a AAA’s length across its diameter.
4. A golf ball (42.7 mm) is almost exactly a AAA’s length.
5. An AirPods case (~53.5 mm tall) is a bit longer than a AAA.
6. A house key (~50 mm) is slightly longer.

AAA Battery Size in Different Units

Why You Can’t Swap AAA and AA

They are the same voltage (1.5 V nominal) and the same chemistry options, but the AAA is 4 mm narrower and 6 mm shorter, so it rattles loose in an AA holder and will not make reliable contact. Spacer adapters exist that turn a AAA into an AA-sized shell, but the AAA still only delivers its smaller capacity, so a device runs for roughly a third to a half as long. Going the other way, an AA simply does not fit a AAA compartment.

Common Mistakes When Comparing AAA Battery Dimensions

1. Assuming a AAA lasts as long as an AA. It has under half the capacity because it has under half the internal volume.
2. Thinking a AAA-in-an-adapter equals an AA. The shell fits, but the runtime is still the AAA’s.
3. Confusing AAA and AAAA. The AAAA is smaller again (42.5 x 8.3 mm) and uncommon.
4. Ignoring the terminal nub in the length. The 44.5 mm figure includes the positive button.
5. Buying “heavy duty” (carbon-zinc) for high-drain devices. In a AAA, alkaline or lithium lasts far longer in cameras and toys.

Frequently Asked Questions

What are the dimensions of a AAA battery?

44.5 mm long and 10.5 mm in diameter.

How much does a AAA battery weigh?

About 11.5 g for alkaline, ~7.6 g for lithium, ~14 g for NiMH.

Is a AAA smaller than a AA?

Yes, 6 mm shorter and 4 mm narrower, and about half the weight.

Can I use a AAA instead of an AA?

Only with a spacer adapter, and the device will run much less time because a AAA holds far less energy.

What is the IEC name for a AAA battery?

R03 for carbon-zinc, LR03 for alkaline, FR03 for lithium, HR03 for NiMH.

Why does a AAA hold less power than an AA?

It has less than half the internal volume for the same chemistry.

Final Takeaway

A AAA battery is 44.5 mm long and 10.5 mm across (IEC R03), with alkaline cells weighing about 11.5 grams. It shares the AA’s 1.5 V and chemistry but holds under half the energy, so a AAA in an AA adapter fits the slot but runs the device for a fraction of the time.