Battery Sizes Explained: AA, AAA, C, D, 9V, Coin Cells & Device Batteries

Batteries come in a bewildering array of shapes, codes, and chemistries—and grabbing the wrong one means a trip back to the store or a device that won't power on. This guide demystifies the most common battery types so you can confidently find the right replacement.

Household "Cylindrical" Sizes

These are the everyday batteries that power remotes, toys, flashlights, and clocks. The size refers to physical dimensions, not brand:

  • AAA – slim and small; remotes, small flashlights, computer peripherals.
  • AA – the most common size; toys, game controllers, wireless mice.
  • C – medium cylinder; larger flashlights, radios, some toys.
  • D – large cylinder; lanterns, big flashlights, boom boxes.
  • 9V – the rectangular battery with snap terminals; smoke detectors and instruments.

All of these are nominally 1.5 volts (the 9V being the exception at 9 volts). They come in alkaline, lithium, and rechargeable NiMH versions—more on chemistry below.

Coin & Button Cells

The small round batteries in watches, car key fobs, bathroom scales, and motherboards are coin cells. Their codes encode their size: a CR2032 is 20 mm wide and 3.2 mm thick, while a CR2025 is the same width but thinner. The "CR" indicates lithium chemistry (3 volts), and "LR"/"SR" indicate alkaline or silver-oxide button cells (1.5V). Always match the full code—a 2032 and a 2025 look nearly identical but aren't always interchangeable.

Understanding Battery Chemistry

Size tells you if a battery fits; chemistry tells you how it performs:

  • Alkaline – inexpensive, great for everyday low-drain devices.
  • Lithium (primary) – lighter, longer-lasting, performs in extreme temperatures; ideal for cameras and smoke detectors.
  • NiMH rechargeable – reusable hundreds of times; best for high-drain devices like game controllers and flashes.
  • Lithium-ion rechargeable – the high-capacity packs inside laptops, phones, and power tools.

Device-Specific Batteries

Beyond standard sizes, most modern electronics use custom battery packs matched to the exact make and model. The trick is finding the right one by your device—or by the part number printed on the old battery. We organize ours by what they power:

How to Find Your Exact Replacement

For device batteries, the surest method is to check the part or model number—usually printed on the battery itself or inside the battery compartment. Searching that number finds an exact-fit replacement. For cylindrical and coin cells, just match the size code (AA, CR2032, etc.) and pick your preferred chemistry.

Storage & Safety Tips

Store batteries at room temperature in their original packaging, keep loose batteries away from coins and keys that could short them, and never mix old and new batteries in the same device. Coin cells must be kept away from children and pets—if swallowed, they're a medical emergency. Recycle rechargeable and lithium batteries at a proper drop-off rather than the trash.

Need Help?

If you're unsure which battery your device takes, find the part number and search it on our site, or browse by device category above. Any term tripping you up? The Batteries & Bulbs Glossary explains the codes and chemistries in plain language.

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