What Size Wrench Do I Need for an Oil Drain Plug?

If you’re wondering what size wrench you need for an oil drain plug, you’re in the right place. In this blog post, we’ll tell you everything you need to know about finding the right wrench size for your oil drain plug.

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Understanding Wrench Sizes

Most wrenches are sized according to the distance, in inches or millimeters, across the flats of the wrench opening. This is known as the “flat size” and is always stamped on the wrench. The oil drain plug on your car is most likely a 13/16-inch or 21 mm wrench. But how do you know for sure without looking it up? There’s an easy way to measure it.

Standard vs. Metric

There are two types of wrenches: standard and metric. Standard wrenches are used in the United States and are measured in inches. Metric wrenches are used everywhere else in the world and are measured in millimeters. Most oil drain plugs use a metric wrench, so if you live in the United States, you will probably need a metric wrench to remove your oil drain plug.

SAE vs. Metric

Two types of standards are used for wrench sizes, SAE (Society of Automotive Engineers) and metric. Most wrenches are one or the other, but some sets include wrenches of both types. To determine which size you need, first identify the type of fastener (nut or bolt) you’re working with. If it’s a bolt, measure the distance across the flats (not the overall length). This measurement is called the “bolt diameter.” For a nut, measure the distance across its outside flats. This measurement is called the “nut diameter.”

The next step is to find a wrench that’s close to those measurements. Wrenches are available in a variety of sizes, so you might have to try several before you find one that fits snugly without being too tight or too loose. If a wrench is too small, it will round off the corners of the fastener. If it’s too big, it won’t fit at all.

Once you’ve found the right wrench size, check to see if there are any other markings on it. Most wrenches have two numbers: one that indicates the wrench size and another that indicates the type of fastener (nut or bolt) it’s meant to be used with. The first number is always going to be either an SAE (inch) size or a metric (millimeter) size. The second number is going to be either 5, 6, 8, 10 or 12; this number corresponds to the type of fastener as follows:

5 = 5/16-inch bolt or 3/8-inch nut
6 = 3/8-inch bolt or 7/16-inch nut
8 = 1/2-inch bolt or 9/16-inch nut
10 = 5/8-inch bolt or 3/4-inch nut
12 = 3/4-inch bolt or 7/8-inch nut

Oil Drain Plug Size

Finding the right size wrench for an oil drain plug is important. If the wrench is too small, it can round off the corners of the plug. If the wrench is too large, it can strip the threads on the plug. In either case, you won’t be able to remove the drain plug and will have to replace it. The size of the wrench you need depends on the size of the oil drain plug.


If you own a car, you should know how to change your own oil. It’s a simple process that anyone can do with the proper tools. One of the most important things you need is the right size wrench for your oil drain plug.

The size of your oil drain plug will depend on the make and model of your car. Most newer cars have a 3/8-inch drain plug, but some older models may have a smaller or larger size. You can usually find the right size in your owner’s manual or by doing a quick search online.

Once you know the size of your drain plug, you can purchase the appropriate sized wrench. Be sure to get one that fits snugly so you can avoid stripping the threads on your drain plug. With the right tools, changing your own oil is quick and easy!


The most common oil drain plug size is 1/2-inch. This is the size of wrench you’ll need to remove most types of oil drain plugs. If your vehicle has a smaller oil drain plug, you’ll need a 3/8-inch wrench. If your vehicle has a larger oil drain plug, you’ll need a 3/4-inch wrench.


Most newer cars use a 9/16-inch drain plug, but some older cars used a 1/2-inch plug. It’s a good idea to check your car’s owner’s manual before you buy a wrench. You can also measure the current drain plug to see what size you need.

Other Oil Drain Plug Sizes

Before you can replace an oil drain plug, you need to know what size wrench to use. If you don’t have the right size wrench, you could strip the oil drain plug and cause serious damage. In this article, we’ll discuss other oil drain plug sizes so that you can be prepared for any situation.


8mm is a popular size for oil drain plugs. Many newer vehicles take an 8mm socket or wrench to remove the oil drain plug. Although 8mm is a standard size, some oil drain plugs may be slightly larger or smaller. It is always best to check your vehicle’s owner’s manual to be sure which size you need.


The 10mm oil drain plug wrench is one of the more common sizes. It is used on many Honda and Toyota vehicles, among others. If you are not sure what size you need, it is always best to check your owner’s manual or take a look at the old plug to be sure.


The 12mm oil drain plug wrench is one of the most common sizes. It is used on many small engines, such as lawnmowers, chain saws, and snow blowers. The 12mm oil drain plug wrench is also used on some cars and trucks.