Socket Set Sizes Chart: SAE and Metric in Order

On this page (7 sections)

1. What does a socket set sizes chart show?
2. Are SAE and metric sockets interchangeable?
3. How do you choose the right socket size?
4. What do standard and deep sockets do?
5. How do socket drive sizes affect your choice?
6. What should you check before buying a socket set?
7. Which socket sizes should you keep on hand?

A socket set sizes chart shows SAE sizes in inches and metric sizes in millimeters. Match the socket's opening to the fastener, since nearby sizes usually aren't exact substitutes.

Use the charts below to compare common sizes, but treat them as a reference rather than a promise that every set includes every size. If you're unsure what range to buy, start with what size socket set you need.

What does a socket set sizes chart show?

A socket set sizes chart lists the opening size that fits a fastener head. Metric sockets are marked in millimeters; SAE sockets are marked in fractions of an inch.

The socket's size is separate from its drive size, which connects it to a ratchet. A 10 mm socket might have a 1/4 in, 3/8 in, or 1/2 in drive, depending on the socket.

Socket set sizes chart: common metric sizes

Metric sockets are sized in millimeters. The chart shows a practical selection of common sizes, not every size made.

The inch column converts the measurement; it doesn't recommend an SAE socket. For example, 10 mm converts to about 0.394 in, while 3/8 in is 0.375 in, so they don't fit the same way.

Socket set sizes chart: common SAE sizes

SAE sockets are sized in fractions of an inch. These common sizes give you a quick reference when a fastener or tool calls for SAE.

The conversions can look close to familiar metric sizes, but a rounded conversion doesn't establish that a socket fits. Use the specified size and stop if the socket rocks or slips.

Are SAE and metric sockets interchangeable?

Nearby SAE and metric sizes usually aren't interchangeable. A loose fit can round a fastener, and a tight fit may not seat all the way.

For example, 1/2 in is 12.7 mm, between common whole-number metric sizes. A 13 mm socket may seem close, but the extra clearance can matter under force.

Use the size specified in the service instructions when possible. If you're deciding which system to buy, our SAE or metric socket set guide explains when a set with both systems makes sense.

How do you choose the right socket size?

Use the specified size and check that it fits snugly over the fastener without rocking. Seat it fully and keep it square before turning.

If the socket doesn't fit, don't force it with a ratchet. Check the measurement system and inspect the fastener for dirt, rust, or damage before trying another size.

A 6-point socket has an opening shaped for a hex fastener, while a 12-point socket offers more starting positions on a hex head. If you're working with worn or stubborn fasteners, see 6-point vs 12-point sockets for the trade-offs.

How do you tell metric from SAE sockets?

Metric sizes are marked in millimeters, such as 8 mm or 14 mm. SAE sizes are marked with inch fractions, such as 5/16 in or 3/4 in.

Markings can be small, so use good light and check the socket itself rather than guessing from its outer size. Some sets store both systems together, making clear labels especially useful.

What do standard and deep sockets do?

Standard sockets suit many everyday fasteners; deep sockets provide more clearance for nuts on longer exposed studs. The right depth depends on how far the stud extends and how much access you have.

A standard socket may bottom out against a stud before gripping the nut. A deep socket adds clearance, but can be too long for a tight space.

The GEARWRENCH 56-piece 6-point socket set includes standard and deep SAE and metric sockets, with hard-stamped size markings.

This 3/8 in drive set includes sizes from 1/4 to 1 in and 6 to 19 mm. GEARWRENCH says its off-corner loading design helps reduce fastener rounding.

For sockets and other tools in one case, the Amazon Basics 201-piece mechanic's socket set includes 1/4, 3/8, and 1/2 in drive sockets in SAE and metric sizes.

Consider how you'll store and carry the tools, too. If you want to understand how those drive sizes differ, read socket drive sizes explained.

How do socket drive sizes affect your choice?

Drive size is the square connection between a socket and a ratchet, not the socket opening. Common drives include 1/4, 3/8, and 1/2 in.

A socket and ratchet must have matching drive sizes, unless you use a suitable adapter. Choose tools rated for the task, since an adapter doesn't increase the load a smaller drive can handle.

Don't choose a socket by drive size alone. A 3/8 in drive socket could have a 10 mm or 3/4 in opening, and those openings fit different fasteners.

The Craftsman 83-piece mechanics tool set combines sockets with 1/4 and 3/8 in drive ratchets, plus specialty bits and hex keys.

The Craftsman 230-piece mechanics tool set includes 1/4, 3/8, and 1/2 in drives, plus SAE and metric sockets, wrenches, hex keys, and specialty bits.

What should you check before buying a socket set?

Check which measurement system, socket range, drive sizes, and socket depths the set includes. Then compare that range with the fasteners you expect to handle.

A dual-system set can be useful if you work on different equipment, but a large piece count alone doesn't tell you whether the key sizes are present. Check for gaps in the range that matter to your jobs.

Also consider the case, size markings, and whether you need standard or deep sockets. For a fuller list of the tools that belong in a kit, see mechanics tool sets.

Which socket sizes should you keep on hand?

Keep the sizes that match the fasteners you work with most. For many home and garage jobs, that means selecting a practical range in the measurement system your equipment uses.

Use this socket set sizes chart as a starting point, then verify fit at the fastener. Choose a set with the needed sizes and compatible drives; see how to use a socket set for setup and fit checks.

If your work uses both systems or several drive sizes, a set that includes both can reduce the need to fill gaps later. If your fasteners use one system, focus on its size range and the socket depths you need.

Frequently asked questions

What are the most common socket sizes?

Common metric sockets include 8, 10, 12, 13, 14, 17, and 19 mm; common SAE sizes include 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, and 3/4 in. The sizes you need depend on the fasteners in your work, so check those before choosing a set.

Are SAE and metric sockets interchangeable?

Usually not: SAE sizes use inches, while metric sizes use millimeters, and nearby sizes often differ enough to affect fit. A socket that is slightly too large can slip and round a fastener, so use the specified size rather than choosing by a rounded conversion.

How do I read socket sizes?

Read the stamped size on the socket, then check whether it uses millimeters or fractions of an inch. Metric sizes use whole or decimal millimeters, such as 10 mm, while SAE sizes use fractions, such as 3/8 in; match that opening to the fastener head.

What is the difference between socket size and drive size?

Socket size is the opening that fits the fastener, such as 10 mm or 3/8 in. Drive size is the square connection between the socket and ratchet, commonly 1/4, 3/8, or 1/2 in, so you need both the correct opening and a compatible drive.