Standard to Metric Socket Conversion Chart
Use this chart to simplify your socket conversions and to streamline your socket size selection, from Standard to Metric.
Note: If a socket is not slightly larger than the bolt it is attempting to work on, it won't fit. That's why all "closest" metric sockets are all slightly larger than the socket being converted from.
Exact conversion values are below the chart. There are no exact match identical socket sizes between metric and standard measurement systems.
Socket Conversion Chart
Metric to Standard | Standard to Meteric
| From Standard | To Metric Socket |
|---|---|
| 1/16" | 2 mm |
| 1/8" | 4 mm |
| 3/16" | 5 mm |
| 1/4" | 7 mm |
| 5/16" | 8 mm |
| 3/8" | 10 mm |
| 7/16" | 12 mm |
| 1/2" | 13 mm |
| 9/16" | 15 mm |
| 5/8" | 16 mm |
| 11/16" | 18 mm |
| 3/4" | 20 mm |
| 13/16" | 21 mm |
| 7/8" | 23 mm |
| 15/16" | 24 mm |
| 1" | 26 mm |
| 1 1/16" | 27 mm |
| 1 1/8" | 29 mm |
| 1 3/16" | 31 mm |
| 1 1/4" | 32 mm |
| 1 5/16" | 34 mm |
| 1 3/8" | 35 mm |
| 1 7/16" | 37 mm |
| 1 1/2" | 39 mm |
| 1 9/16" | 40 mm |
| 1 5/8" | 42 mm |
| 1 11/16" | 43 mm |
| 1 3/4" | 45 mm |
| 1 13/16" | 47 mm |
| 1 7/8" | 48 mm |
| 1 15/16" | 50 mm |
| 2″ | 51 mm |
Common Socket Conversions
For common inch to mm socket conversions the conversion formula is 25.4 millimeters(mm) per inch. (For spark plug info visit the spark plug socket size page.)
1/16" Socket to mm
1/16 x 25.4 = 1.5875 mm. The closest equivalent Metric size socket is 2mm.
1/8" Socket to mm
1/8 x 25.4 = 3.175 mm. The closest equivalent Metric size socket is 4mm. (3mm would be too small to fit a 1/8 bolt)
3/16" Socket to mm
3/16 x 25.4 = 4.7625 mm. The closest equivalent Metric size socket is 5mm.
1/4" Socket to mm
1/4 x 25.4 = 6.35 mm. The closest equivalent Metric size socket is 7mm.
5/16" Socket to mm
5/16 x 25.4 = 7.9375 mm. The closest equivalent Metric size socket is 8mm.
3/8" Socket to mm
3/8 x 25.4 = 9.525 mm. The closest equivalent Metric size socket is 10mm.
7/16" Socket to mm
7/16 x 25.4 = 11.1125 mm. The closest equivalent Metric size socket is 12mm.
1/2" Socket to mm
1/2 x 25.4 = 12.7 mm. The closest equivalent Metric size socket is 13mm.
9/16" Socket to mm
9/16 x 25.4 = 14.2875 mm. The closest equivalent Metric size socket is 15mm.
5/8" Socket to mm
5/8 x 25.4 = 15.875 mm. The closest equivalent Metric size socket is 16mm.
11/16" Socket to mm
11/16 x 25.4 = 17.4625 mm. The closest equivalent Metric size socket is 18mm.
3/4" Socket to mm
3/4 x 25.4 = 19.05 mm. The closest equivalent Metric size socket is 20mm. a slightly worn 19mm socket may also fit a 3/4 inch bolt.
13/16" Socket to mm
13/16 x 25.4 = 20.6375 mm. The closest equivalent Metric size socket is 21mm.
7/8" Socket to mm
7/8 x 25.4 = 22.225 mm. The closest equivalent Metric size socket is 23mm.
15/16" Socket to mm
15/16 x 25.4 = 23.8125 mm. The closest equivalent Metric size socket is 24mm.
1" Socket to mm
1 x 25.4 = 25.4 mm. The closest equivalent Metric size socket is 26mm.
1 1/16" Socket to mm
1 1/16 x 25.4 = 26.9875 mm. The closest equivalent Metric size socket is 27mm.
1 1/8" Socket to mm
1 1/8 x 25.4 = 28.575 mm. The closest equivalent Metric size socket is 29mm.
1 3/16" Socket to mm
1 3/16 x 25.4 = 30.1625 mm. The closest equivalent Metric size socket is 31mm.
1 1/4" Socket to mm
1 1/4 x 25.4 = 31.75 mm. The closest equivalent Metric size socket is 32mm.
1 5/16" Socket to mm
1 5/16 x 25.4 = 33.3375 mm. The closest equivalent Metric size socket is 34mm.
1 3/8" Socket to mm
1 3/8 x 25.4 = 34.925 mm. The closest equivalent Metric size socket is 35mm.
1 7/16" Socket to mm
1 7/16 x 25.4 = 36.5125 mm. The closest equivalent Metric size socket is 37mm.
1 1/2" Socket to mm
1 1/2 x 25.4 = 38.1 mm. The closest equivalent Metric size socket is 39mm.
1 9/16" Socket to mm
1 9/16 x 25.4 = 39.6875 mm. The closest equivalent Metric size socket is 40mm.
1 5/8" Socket to mm
1 5/8 x 25.4 = 41.275 mm. The closest equivalent Metric size socket is 42mm.
1 11/16" Socket to mm
1 11/16 x 25.4 = 42.8625 mm. The closest equivalent Metric size socket is 43mm.
1 3/4" Socket to mm
1 3/4 x 25.4 = 44.45 mm. The closest equivalent Metric size socket is 45mm.
1 13/16" Socket to mm
1 13/16 x 25.4 = 46.0375 mm. The closest equivalent Metric size socket is 47mm.
1 7/8" Socket to mm
1 7/8 x 25.4 = 47.625 mm. The closest equivalent Metric size socket is 48mm.
1 15/16" Socket to mm
1 15/16 x 25.4 = 49.2125 mm. The closest equivalent Metric size socket is 50mm.
2" Socket to mm
2 x 25.4 = 50.8 mm. The closest equivalent Metric size socket is 51mm.
Remember: These are approximate equivalents rounded to the nearest metric socket size that will fit nuts and bolts.
Also: Use the Inch-lbs to Foot-lbs guide for help with torque wrench sockets and settings.
Test the Socket Conversion
After you've completed the conversion process, give the converted socket a try! Attach it to your wrench, gently tighten a bolt, and see how it feels.
If you think it feels too loose, trust your instincts. Applying pressure on a loose socket can cause damage and injury.
Quick Tip: If it feels a bit loose, try covering the bolt with a shop cloth before attaching the socket. Keep in mind, this works best with lighter torque.
Ensure that the socket securely grips the fastener without slipping, and verify that it doesn't round off the edges.
