AA vs D

Both 1.5 V alkaline. At 34.2 × 61.5 mm against 14.5 × 50.5 mm, the D holds roughly six times the energy of an AA.

Quick answer

Both give 1.5 volts. The D is much larger and holds around six times as much energy, so it runs far longer between changes — that is the entire difference. They are not interchangeable: a D is more than twice the width of an AA and a centimetre longer. Adapter sleeves let an AA sit in a D compartment, but you get AA runtime, not D runtime, and less current with it.

Verdict:: Same 1.5 V, roughly six times the runtime
Interchangeable:: no

Side-by-side specifications

AA compared with D
Specification	AA	D
Chemistry	Alkaline	Alkaline
Type	Cylindrical	Cylindrical
Nominal voltage	1.5 V	1.5 V
Diameter	14.5 mm	34.2 mm
Height	50.5 mm	61.5 mm
Typical capacity	1800–2900 mAh	12000–18000 mAh
Rechargeable	No	No
Also sold as	LR6, MN1500, AM3, R6	LR20, MN1300, AM1, R20

Size comparison

Ø 14.5 mm · H 50.5 mm

Ø 34.2 mm · H 61.5 mm

These cells do not share a footprint, so one will not sit correctly in the other's compartment.

Size

34.2 × 61.5 mm against 14.5 × 50.5 mm. The D is the largest of the common household cells and does not share a compartment with anything else.

Runtime

12000–18000 mAh against 1800–2900 mAh — around six times the reserve, which is why lanterns and floor sweepers are built around it.

Current, not just capacity

A larger cell also sustains a higher current. Devices that specify D cells often need that, so an AA in an adapter can sag under load even where it physically works.

Can I use a D instead of a AA?

Not directly. The D measures 34.2 × 61.5 mm against 14.5 × 50.5 mm for the AA, so it will not seat properly in the same compartment.

AA specs →D specs →

Check before you swap. Batteries with similar dimensions are not always interchangeable. Always verify voltage, chemistry and the requirements printed in your device manual before fitting a replacement.

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