Battery Group Size: What It Is and Why It Matters

Like shoes, car batteries come in a range of sizes, styles, and fits.

Ronan Glon | 
Sep 5, 2023 | 3 min read

Car battery beneath open truck hoodAustin Lott | Capital One

Updated on 9/19/2023

When you're looking to replace your battery, you should take into account specifics such as the battery's shape, how it fits into your vehicle, and how powerful it needs to be.

Size is just one of the factors to keep in mind when shopping for a new car battery. You can use a battery group size chart to figure out which sizes are standard, but the physical dimensions of a battery are just one of a few factors that are important.

What Is a Battery Group Size?

Although car batteries all perform the same functions, they come in several shapes and sizes. Battery Council International created a group size chart to take some of the guesswork out of shopping for a new battery by assigning a specific set of dimensions and a size number. The resource is a bit like a shoe-size chart for car batteries. For example, a size 34 battery is 10 1/4 inches long, 6 13/16 inches wide, and 7 7/8 inches high, regardless of brand or cost.

Just as you'd try on a pair of shoes to ensure a proper fit, you should find the correct battery group size for your car, because a battery that's too big might not physically fit in your vehicle. Even if you could shoehorn a bigger battery into your car or truck, you might not be able to properly secure it using the , meaning the battery could move around on a bumpy or twisty road or in an accident.

Where to Find Your Car's Battery Group Size

Your vehicle's owner's manual typically provides the battery group size. If that information isn't listed there, ask your local dealership's service department or a parts store. The battery size should also appear on the battery in your car, but double-check that the battery in your vehicle is the correct size before buying the same thing. Many battery manufacturers make this information accessible online as well.

What Else to Consider When Buying a Battery

Most of the batteries installed in new and late-model cars feature a pair of  labeled positive and negative. Still, some vehicles require a battery with side-mounted terminals.

These battery types aren't interchangeable. Top-mounted terminals might not clear the hood in a car designed to take a battery with side-mounted terminals, and it could be impossible to secure the battery cables if you order the wrong type. You can generally find this information by looking at the battery in the owner's manual or online or by examining the way your current battery is hooked up.

What's inside the battery is also important. There are several battery types available, including lead-acid and absorbed glass mat. It's important to determine which kind your vehicle needs. Another key part of the battery is its cold-cranking amp rating, which concerns how many amps a battery can deliver to help start a car engine in cold weather.

Even if a battery fits into your car, it might not be powerful enough to start the engine on a cold day. Remember that a battery's physical size isn't always proportional to its cold-cranking amps or starting power.

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Ronan Glon

Ronan Glon is an American journalist and automotive historian based in France. He enjoys working on old cars and spending time outdoors seeking out his next project car.