How to Use the Battery Size Guide
Batteries differ in more than just physical size — voltage and capacity vary by type too, and putting the wrong one in a device can mean it won't run properly or drains far faster than expected. Select a battery type above to see its standard voltage, typical capacity in mAh, and the devices it's most commonly used in.
AA and AAA are both 1.5V, but AA is larger and holds more capacity, making it the better choice for higher-drain devices like flashlights or wireless mice, while AAA suits low-drain items such as remote controls. C and D batteries are considerably bigger with much higher capacity, typically found in lanterns and large radios. A 9V battery serves devices that need a specific higher voltage, like smoke detectors and guitar pedals, while the small CR2032 coin cell powers watches and key fobs. Rechargeable 18650 cells run at 3.7V — noticeably different from standard alkaline batteries — so always confirm compatibility before using one as a substitute.
Frequently Asked Questions
Both are 1.5V, but AA batteries are physically larger and hold more capacity (mAh) than AAA. AA is better for higher-drain devices, while AAA suits low-drain items like remote controls.
In most devices, yes. Rechargeable NiMH batteries run at 1.2V instead of the 1.5V of alkaline batteries, so devices that need precise voltage may show a slight performance difference.