Metric versus SAE (Standard) Sockets:

The difference between Metric and SAE sockets is similar to the difference between yards and meters. Metric fasteners are (generally) used on imported cars, and SAE fasteners are (generally) used on domestic (USA) made cars. Also, they are two completely different systems of measurement. Metric sockets use the metric measurement system i.e., millimeters to describe their size (e.g., an 18mm socket). SAE, or standard size, use the imperial measurement system we invented in the USA. Therefore, sockets are described in fractions of an inch, i.e., 1/2″ socket. Make no mistake however, in 2020, you will find metric and SAE fasteners on domestic cars. Unless you are working on solely older American cars, you will find yourself using your Metric sockets 9/10 times.

Sometimes a metric fastener is close enough in size that an SAE socket may work and vice versa for metric sockets on SAE fasteners. While there are some very close crossover sockets between Metric and SAE, I would advise you to avoid substituting sockets or tools in general between the tool systems.

You want to try to avoid using metric sockets on SAE fasteners, and SAE sockets on metric fasteners. The simple reason is that while it may feel like it fits okay, many times you risk a higher chance of stripping the bolt or fastener using the wrong socket.

Pro tip: Be careful, and use my guide listed below to see what fasteners are usually close enough metric and SAE to use the same sockets/wrenches.

SAE and Metric Have Historical Beef:

SAE stands for Society of Automotive Engineers and the sockets are typically marked in fractions of an inch, i.e., 1/2″, 3/8″, 13/16″. Metric tools are measured in millimeters and come in sizes such as 8 mm, 10 mm, 12 mm, etc. Fasteners, or bolts and nuts, are also different for SAE and Metric sizes, with SAE bolts being referred to in fractions of an inch (like the sockets) and metric bolts and nuts being referred to in millimeters. For example, you might hear a mechanic yell “Hey, I need a 9/16″ bolt for the Ford and a 12mm nut for the Honda.”

If you’re going to be working on both types of cars, foreign and domestic, you will need both SAE sockets and metric sockets. However, the general trend is moving away from SAE fasteners and more companies are going 100% metric. This also includes Ford, Dodge, and most “Domestic” car brands that are actually made with mostly oversea’s parts or built in Mexico. They are moving towards using mostly metric sizes as well. 

Why do no metric drive sizes exist:

Both metric and SAE sockets are available in three drive sizes: ¼”, 3/8″ and ½”. Interestingly enough because the original ratchet was an American invention, metric sockets still use imperial sized drivers. The drive dimensions always followed the US sizes, 1/4″, 3/8″, 1/2″, 3/4″ drives to be exact. This really is great for you, because it means one less thing to have buy another set for. It would be a real pain if metric sockets also had their own special ratchets with metrically sized drivers. We can thank our lucky stars this isn’t the case.

Smaller sockets typically use smaller drive sizes, while larger sockets use the larger drive sizes. For example, a 6mm socket (relatively small for automotive repair) will most commonly be sold in the 1/4″ drive size.

Common sizes for metric sockets:

The most common sizes for metric sockets for automotive repair are 8mm to 19mm sockets. You will most commonly find socket sets that are sold that contain all the sockets between 8mm to 19mm. Most metric socket sets, wrenches, and flare nut wrenches will contain these metric sizes (6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm.) The absolute most commonly used socket for any car repair is the 10mm socket. Followed closely by 12mm, 14mm, 17mm, and 19mm sockets. You should have a high-quality set of metric sockets for all the different drives, or at least adapters, and separate lug nut sockets.

There are also some common metric sized bolts that require larger metric socket sizes as well. On many imported cars, you will find the lug nuts will commonly be 19mm or 21mm. However, on some cars or trucks, the lug nuts will require even larger metric sockets, and you should be prepared and have those sizes.

Common sizes for SAE / Imperial / Standard sockets:

The most commonly used and sold SAE sizes for wrenches and sockets are: 

• Standard socket sizes 5/16″, 3/8″, 7/16″, 1/2″, 9/16″, 5/8″, 11/16″, 3/4″, 13/16″, 7/8″, 1″, 1-1/4″, 1-7/16″, 1-1/2″ etc. Any larger than around 7/8″ is usually on an as needed basis. Unless you are working on heavy-duty trucks or cars, then you should get a set that goes all the way up the 1-1/4″ or larger. 

Depending on what kind of cars, motorcycles, scooters you are working on there are some SAE sockets that may come in handy. Although, as many technicians will tell you the number is dropping fast. You can usually get by without many SAE wrenches and sockets, but when you do need them you’ll be happy you have a set.

I would say unless you’re working on domestic cars only, start with metric sets first. Maybe grab one SAE socket set, then fill in wrenches, etc as you find you need. Otherwise, don’t spend your money on SAE tools until you see whether you need them or not. Metric are becoming much more common on all things cars, motorcycles, and even domestic trucks.

Common metric lug nut sizes and the kinds of cars that use them:

17mm Euro

21mm Most of Toyota’s (Common)

19mm Volvo, Subaru’s, Some Honda’s, Some Domestic Cars (Very common size)

22mm Chevy Fullsize New Honda’s Ford van’s

22m for many Ferrari’s

23mm Dodge Fullsize Trucks

27mm *weird one* for Land Rover’s

Lugnut sockets need to have a protective soft coating. That way you don’t ruin your rims by scratching them with the sides of the socket.

A lot of companies these days are making really cool reversible lug nut socket sets (so there are two different lug nut sockets built into the same socket).

When you are searching to buy a lug nut socket set make sure it has the sizes you’ll need for the majority of cars you will be working on. I recommend buying the Chicago Pneumatic Lug Nut Socket Set that includes 11 sockets that meet all the most common SAE and metric lug nut sizes.  

The kit comes with these 1/2″ drive sockets 3/4, 13/16, 7/8, 15/16, 1, 1-1/16 in., 17mm, 19mm, 21mm, 22mm and 23mm. If you do have a weird Land Rover you will need to get a separate 27mm socket for those lug nuts. 

You will also need large metric sockets for Axle Nuts:

If you will be swapping CV axles on any cars you will need to have larger sockets. These nuts commonly referred to as spindle nuts, hub nuts, or axle nuts typically use pretty large sockets. Any front wheel drive car (or 4×4) will have a CV axle nut.

For the purposes of this discussion, I will be using hub nut/spindle nut/axle nut/axle drive nut/ to mean the same thing. The nut that holds the CV axle to the hub.

Common axle nut/spindle nut sizes / here is what I found: 

Honda mostly uses 32mm axle and spindle nut sizes.

Small Chevys and Toyotas use 30 mm.

Mitsubishi likes to use 32 mm.

Volkswagens are mostly 30 mm 12 point nuts. (1993+ VW’s went up to 12point spindle nut size) You will need a 12 point 30mm socket to remove.

C5 and C6 Corvettes use a 34 mm spindle nut.

Mid 90’s BMW’s need a 46mm socket to remove the hub nut.

Honda JDM Type R’s require a 36mm Socket

30mm 32mm or 36mm on Nissan’s depending on year make and model.

General Motors (GM) 1/2 ton trucks front cv axle is a 34mm or 36mm

Kia’s Spindle Nut size: 35-36mm

Mazda 30mm, 32mm, 35mm (a bit of a weird one) on some

Toyota Tundra’s, Landcruiser, and Highlander 39mm socket (also an uncommon size) front axle nut size

Astro Vans: 27mm (weird one) front axle nut size. 

To check out a really cool chart that includes most vehicles and the spindle nut sizes click here.

To find out what spindle nut size your car or truck has just google it. Here’s how to do phrase it:

“Your (Make, model and year) CV axle nut size). Then order the right socket for your vehicle.

Axle Nut Socket Set Buying Guide:

If you’re looking for a good axle nut socket set to buy I did some research and found that these sets are the best value.

1. OEM TOOLS 24480 12 Point Axle Nut Socket Set (8 Piece)
   • 1/2″ Drive / Impact Rated / Well Reviewed
   • 29, 30, 32, 34, 35, 36, 38 and 39 mm sizes (Look above that covers 90% what you need)
   • Comes with a sturdy plastic case making transport easier.
   • Click here to read current reviews and get the price.
2. Astro Pneumatic Tool 12-Point Axle Nut Socket Set (8 Piece) *Slightly More Expensive*
   • Designed for an exact fit on both 6pt and 12pt axle nuts (I am pretty sure the OEM TOOLS one will work for both as well). But this is comforting to know they advertise as working for both 6 point and 12 point CV axle spindle nuts.
   • 1/2″ drive Impact Drive
   • Includes large 39mm socket for Toyota/Lexus applications
   • 29mm, 30mm, 32mm, 34mm, 35mm, 36mm, 38mm, 39mm (Exact same as the OEM tools set).
3. If you’re working on mostly Volkswagen and Audi Specific  buy this Axle Nut Socket Set:
   • Assenmacher 6506 6 Piece VW/Audi Axle Nut Socket Set
     • Covers all Volkswagen/Audi axle nuts from [1996-2013].
     • Includes a 14mm and 17mm Allen as well as an 18mm 24mm 30mm and 32mm 12-point sockets