Socket Conversion Chart: Metric and Standard
Standard sockets are measured in inches and metric sockets are measured in millimeters (mm). This socket size chart help with conversion.
If you’ve ever had a socket “almost” fit, and you realize the bolt is from that “other” measurement system, Argh! I get it.
Socket conversion refers to the process of transitioning from one measurement system to another when working with sockets.
Specifically, it involves switching between Standard and Metric socket sizes.
A socket size conversion chart can help you find the best match socket size between Metric and Standard sockets.
Socket size conversion formula: 1 inch = 25.4 millimeters.
| Socket Size Conversion Chart | |||
|---|---|---|---|
| Metric to Standard | Standard to Metric | ||
| Metric | Stnd | Stnd | Metric |
| 4 mm | use a 3/16″ | 1/8″ | use a 4 mm |
| 5 mm | use a 1/4″ | 3/16″ | use a 5 mm |
| 6 mm | use a 1/4″ | 1/4″ | use a 7 mm |
| 7 mm | use a 5/16″ | 5/16″ | use an 8 mm |
| 8 mm | use a 3/8″ | 3/8″ | use a 10 mm |
| 9 mm | use a 3/8″ | 7/16″ | use a 12 mm |
| 10 mm | use a 7/16″ | 1/2″ | use a 13 mm |
| 11 mm | use a 7/16″ | 9/16″ | use a 15 mm |
| 12 mm | use a 1/2″ | 5/8″ | use a 16 mm |
| 13 mm | use a 9/16″ | 11/16″ | use an 18 mm |
| 14 mm | use a 9/16″ | 3/4″ | use a 20 mm |
| 15 mm | use a 5/8″ | 13/16″ | use a 21 mm |
| 16 mm | use an 11/16″ | 7/8″ | use a 23 mm |
| 17 mm | use an 11/16″ | 15/16″ | use a 24 mm |
| 18 mm | use a 3/4″ | 1″ | use a 26 mm |
| 19 mm | use a 3/4″ | 1 1/8″ | use a 29 mm |
| 20 mm | use a 13/16″ | 1 3/16″ | use a 31 mm |
| 21 mm | use a 7/8″ | 1 1/4″ | use a 32 mm |
| 22 mm | use a 7/8″ | 1 5/16″ | use a 34 mm |
| 23 mm | use a 15/16″ | 1 3/8″ | use a 35 mm |
| 24 mm | use a 1″ | 1 7/16″ | use a 37 mm |
| 25 mm | use a 1″ | 1 1/2″ | use a 39 mm |
| 26 mm | use a 1 1/16″ | 1 9/16″ | use a 40 mm |
| 27 mm | use a 1 1/8″ | 1 5/8″ | use a 42 mm |
| 28 mm | use a 1 1/8″ | 1 11/16″ | use a 43 mm |
| 29 mm | use a 1 1/4″ | 1 3/4″ | use a 45 mm |
| 30 mm | use a 1 1/4″ | 1 13/16″ | use a 47 mm |
| 31 mm | use a 1 1/4″ | 1 7/8″ | use a 48 mm |
| 32 mm | use a 1 5/16″ | 1 15/16″ | use a 50 mm |
| 33 mm | use a 1 5/16″ | 2″ | use a 51 mm |
| 34 mm | use a 1 3/8″ | 2 1/8″ | use a 54 mm |
| 35 mm | use a 1 7/16″ | 2 3/16″ | use a 56 mm |
| 36 mm | use a 1 7/16″ | 2 1/4″ | use a 58 mm |
| 37 mm | use a 1 1/2″ | 2 5/16″ | use a 59 mm |
| 38 mm | use a 1 1/2″ | 2 3/8″ | use a 61 mm |
| 39 mm | use a 1 9/16″ | 2 7/16″ | use a 62 mm |
| 40 mm | use a 1 5/8″ | 2 1/2″ | use a 64 mm |
| 41 mm | use a 1 5/8″ | 2 9/16″ | use a 66 mm |
| 42 mm | use a 1 11/16″ | 2 5/8″ | use a 67 mm |
| 43 mm | use a 1 3/4″ | 2 11/16″ | use a 69 mm |
| 44 mm | use a 1 3/4″ | 2 3/4″ | use a 70 mm |
| 45 mm | use a 1 13/16″ | 2 13/16″ | use a 72 mm |
| 46 mm | use a 1 13/16″ | 2 7/8″ | use a 74 mm |
| 47 mm | use a 1 7/8″ | 2 15/16″ | use a 75 mm |
| 48 mm | use a 1 15/16″ | ||
| 49 mm | use a 1 15/16″ | ||
| 50 mm | use a 2″ | ||
Tip: Use the chart in combination with our bolt head size chart for best results.
Converting Metric to Standard
When you have a metric socket and need to find its standard size equivalent, simply divide the metric size by 25.4.
Example: if you have a 13 mm socket, dividing 13 mm by 25.4 equals 0.5118 inches.
The closest standard size socket to 0.5118 inches is a 9/16″ socket, as you can see on a socket conversion chart.
Converting Standard (SAE) to Metric
When you have a standard socket and need to find its metric size equivalent, simply multiply the standard size by 25.4.
Example: a 3/8″ socket, multiplied by 25.4, equals 9.53 mm.
The closest metric size socket size to 9.53 mm is the 10 mm socket.
To save time, consult the socket conversion chart. It has done the conversion equations for you.
Tip: Keep a copy of the chart with your small engine repair tools for quick reference.
Frequently Asked Questions:
Remember: For a socket to be a best match it must be slightly larger than the socket you are converting from because a smaller socket would not fit.
- Does socket conversion work on wrenches? Socket conversion works on wrenches, however, if a wrench can reach the bolt, so can a measuring tape. This wrench conversion chart includes bolt sizes.
- 36 mm socket converted to standard? A 36 mm socket converted to standard is slightly smaller than 1 7/16″. This means a 1 7/16″ socket is the best match for a 36 mm socket.
- 42mm socket to standard? A 42mm socket converted to standard is slightly smaller than a 1 11/16th socket. This means a 1 11/16″ socket is the best match for a 42mm socket.
- 1 7/16 socket to mm? A 1 7/16″ socket converted to metric is slightly smaller than a 37mm socket. This means a 37mm socket is the best match for a 1 7/16″ socket.
- 1 1/16 to mm socket? A 1 1/16″ socket converted to metric is slightly smaller than a 27mm socket. This means a 27mm socket is the best match for a 1 1/16″ socket.
FAQ Updated: May 26, 2023