Battery Size Chart: AA, AAA, C, D, 9V Dimensions 2026

How battery size is worked out

A battery is sized by two numbers: how wide it is and how long it is. The diameter tells you whether it fits the device, and the capacity in milliamp-hours tells you how long it lasts. The table lists the seven common household batteries, smallest first: AAA is 10.5 × 44.5 mm, AA is 14.5 × 50.5 mm, C is 26.2 × 50.0 mm, D is 34.2 × 61.5 mm, 9V is 26.5 × 17.5 × 48.5 mm, CR2032 is 20.0 mm across and 3.2 mm thick, and CR123A is 17.0 mm across and 34.5 mm long. The AA-equivalent is the capacity divided by 2,500, because one AA holds 2,500 mAh — so a D battery, at 12,000 mAh, is 4.80 times an AA, and a CR2032, at 220 mAh, is 0.09 times an AA. The lookup picks the battery by name and returns that row, and the reverse takes a diameter and returns the standard battery with that diameter.

At the defaults — AA, diameter 14.5 mm — the AA is 14.5 × 50.5 mm, 1.5 V, 2,500 mAh, or 1.00× an AA, and it fits remotes, clocks and toys. The reverse of 14.5 mm is the AA itself, the reverse of 10.5 mm is the AAA, the reverse of 34.2 mm is the D, and the reverse of 20.0 mm is the CR2032.

This is a size chart, not a rechargeable, voltage-drop, or battery-life chart: it does not list which batteries can be recharged, how far the voltage falls as the battery drains, or how many hours a battery lasts in a device, because how long a battery lasts depends on what it powers, not just on the battery.

The worked example, line by line

Setup: AA, reverse diameter 14.5 mm.

Line 1 — the size. The AA is 14.5 × 50.5 mm: 14.5 mm across and 50.5 mm long, which is the size the battery compartment is cut for.

Line 2 — the voltage. The AA is 1.5 V, which is the voltage the device is built for: a 1.5 V device takes a 1.5 V battery, not a 3 V or a 9 V one.

Line 3 — the capacity. The AA holds 2,500 mAh, which is the 1.00× reference for the whole chart: every other battery is measured against it.

Line 4 — the reverse. A diameter of 14.5 mm is an AA, a diameter of 10.5 mm is an AAA, a diameter of 34.2 mm is a D, and a diameter of 20.0 mm is a CR2032.

Every branch, checked

AAA: the AAA is 10.5 × 44.5 mm, 1.5 V, 1,000 mAh, or 0.40× an AA. It is the small battery for small devices — TV remotes, small toys and wireless mice — and it holds less than half the charge of an AA.

C: the C is 26.2 × 50.0 mm, 1.5 V, 8,000 mAh, or 3.20× an AA. It is the middle battery for flashlights and toys: about the same length as an AA, but much wider, and it holds more than three times the charge.

D: the D is 34.2 × 61.5 mm, 1.5 V, 12,000 mAh, or 4.80× an AA. It is the big battery for large flashlights and radios, and it holds almost five times the charge of an AA.

9V: the 9V is 26.5 × 17.5 × 48.5 mm, 9 V, 550 mAh, or 0.22× an AA. It is the rectangular battery for smoke alarms and guitar pedals, and it is the only battery in the chart that is not a cylinder.

CR2032: the CR2032 is 20.0 mm across and 3.2 mm thick, 3 V, 220 mAh, or 0.09× an AA. It is the coin battery for watches and key fobs, and it holds less than a tenth of the charge of an AA.

Extra — the D against the AA: one D battery holds 4.80× the capacity of one AA: 12,000 mAh against 2,500 mAh. A device that takes a D lasts far longer on one battery than the same device on an AA would, if it could take one.

Reverse — the diameters: 14.5 mm is an AA, 10.5 mm is an AAA, 34.2 mm is a D, and 20.0 mm is a CR2032. A diameter that matches no standard battery — 25.0 mm, for example — has no standard battery: measure again, or check whether the battery is a less common size.

What the defaults assume

The model assumes the batteries are ordinary alkaline or lithium cells in good condition, the sizes are the standard sizes, and the capacities are the typical capacities for that size. It assumes the device takes the battery the chart lists for it: a device built for an AA takes an AA, and a device built for a D takes a D. It leaves out rechargeable batteries, the voltage drop as the battery drains, and the battery life in hours — this is a size chart, not a rechargeable, voltage-drop, or battery-life chart. Rounding convention: sizes to 1 decimal, capacities to whole milliamp-hours, AA-equivalents to 2 decimals, and all figures are taken from the table, not rounded from other values.

Output · formula · meaning

Who uses this

• The homeowner with a dead remote: they learn an AA is 14.5 × 50.5 mm, 1.5 V, 2,500 mAh — so they know the remote takes an AA, not an AAA, and they buy the right battery the first time.
• The parent with a toy that takes C batteries: they learn a C is 26.2 × 50.0 mm, 1.5 V, 8,000 mAh, 3.20× an AA — so they know the toy needs the wider battery, and they know one C lasts more than three times as long as an AA would.
• The camper with a large flashlight: they learn a D is 34.2 × 61.5 mm, 1.5 V, 12,000 mAh, 4.80× an AA — so they know the flashlight takes the big battery, and they know one D holds almost five times the charge of an AA.
• The driver whose key fob died: they learn a CR2032 is 20.0 mm across and 3.2 mm thick, 3 V, 220 mAh — so they know the fob takes the coin battery, and they measure the old battery to check it before they buy.

Accuracy & limitations

The math is exact for the table: the AA-equivalent is the capacity divided by 2,500, the lookup returns the row for the battery picked, and the reverse returns the standard battery with the diameter entered. What the model cannot do is measure your battery for you: measure the diameter with a ruler or calipers, and check the size printed on the battery itself. It is a size chart, not a rechargeable, voltage-drop, or battery-life chart — it does not say which batteries can be recharged, how far the voltage falls as the battery drains, or how many hours a battery lasts in a device. It assumes the capacities are the typical capacities for that size, and a cheap battery can hold less. For more battery sizes, see battery sizes chart; for the wire inside the device, see AWG wire ampacity chart.