What Size Wrench Do You Need for a Car Battery?

If you’re wondering what size wrench you need for a car battery, you’ve come to the right place. In this blog post, we’ll give you all the information you need to know about finding the right wrench size for your car battery.

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Wrench Sizes

The average car battery is between 10 and 12 inches in length. The most common wrench size for a car battery is a 10mm wrench. However, you may need a different size wrench depending on the make and model of your car.

Standard or Metric

When shopping for a new wrench, you’ll notice that they are available in two different systems, standard or metric. In order to get the right size, you need to know which kind of system your vehicle uses.

Standard wrenches are typically used on older cars and trucks, while metric wrenches are most often found on newer vehicles. You can usually tell which system your vehicle uses by looking at the size of the bolts and nuts. If they are larger, then you will need a standard wrench. If they are smaller, then you will need a metric wrench.

One way to determine this is by looking at the owner’s manual for your vehicle. It should list the sizes of the bolts and nuts that were used when the car was manufactured. Another way to tell is by using a ruler or tape measure to measure the distance across the flats of the bolt or nut. This method is not as accurate as using a caliper, but it will give you a close enough estimate if you don’t have one handy.

Once you know which system your vehicle uses, shopping for a new wrench will be much easier.

SAE (Society of Automotive Engineers)

The vast majority of wrenches you will encounter are SAE, or Society of Automotive Engineers, wrenches. This system uses numbers to indicate the size of the wrench, with the larger numbers indicating a larger wrench. The smallest SAE wrenches are typically 1/4 inch, while the largest are 1 inch. In between these extremes, you will find 3/8 inch, 1/2 inch, 5/8 inch, and 3/4 inch wrenches.

Car Batteries

Car batteries come in different sizes. The most common size is the Group 24, which is about 12 inches long and 6 inches wide. The next most common size is the Group 27, which is about 12 inches long and 7 inches wide. There are also smaller sizes like the Group 22 and the Group 29. You will need a different size wrench for each size battery.

Different battery types

lead-acid batteries
Lead-acid batteries are made of lead and sulfuric acid. The lead reacts with the sulfuric acid to create lead sulfate. The lead sulfate is then converted back to lead and sulfuric acid when the battery is being charged.

lithium ion batteries
Lithium ion batteries are made of lithium, carbon, and other materials. The lithium reacts with the carbon to create lithium carbonate. The lithium carbonate is then converted back to lithium and carbon when the battery is being charged

How to measure a battery

There are a few ways that you can measure a battery. The most common way is to use a voltmeter. You can also use a multimeter set to the DC voltage setting, or an ohmmeter set to the resistance setting.

If you don’t have a voltmeter, you can measure the battery with a ruler. The width of the battery is the width of the case, and the height is the distance from the top of the positive terminal to the bottom of the negative terminal. The length is the distance from the front of the positive terminal to the back of the negative terminal.

Which Wrench to Use

13/16 is the size you need for a car battery, however, you need to make sure that the wrench you are using is the right size. There are three main types of wrenches: standard, metric, and pipe. Standard wrenches are measured in inches and have fractional sizes, such as 1/2, 3/4, or 1. Metric wrenches are metric sizes and are usually in millimeters.

10mm or 3/8″

There are a variety of wrenches that can be used for a car battery, but the most common size is 10mm or 3/8″. This size wrench will allow you to loosen and tighten the battery terminals without putting too much strain on the battery.

12mm or 1/2″

For most car batteries, you’ll need a 12mm or 1/2″ wrench. This size is typically marked on the battery terminal cover. Once you’ve located the right size, simply loosen the nut or bolt until it can be removed by hand.


It’s important to know what size wrench you need for a car battery, because if you don’t have the right size, you could damage the battery terminals. The most common size wrench for a car battery is 10mm, but it’s always a good idea to check your specific car’s manual to be sure.