SAE to Metric Conversion Chart (Wrench & Socket Sizes)
SAE to Metric Conversion Chart (Wrench & Socket Sizes)
Grabbing the wrong-size socket wastes time and rounds off bolts. This SAE-to-metric conversion chart lists every common standard (inch) wrench and socket size with its exact metric (mm) equivalent, so you can find the right tool fast — and know which sizes are close enough to swap in a pinch.
SAE to metric conversion chart
Standard (SAE) sizes are measured in inches; metric sizes in millimeters. Here's every common size, smallest to largest, with the exact conversion (1 inch = 25.4 mm):
| SAE (inch) | Decimal (inch) | Metric (mm) |
|---|---|---|
| 1/4" | 0.250 | 6.35 mm |
| 5/16" | 0.3125 | 7.94 mm |
| 3/8" | 0.375 | 9.53 mm |
| 7/16" | 0.4375 | 11.11 mm |
| 1/2" | 0.500 | 12.70 mm |
| 9/16" | 0.5625 | 14.29 mm |
| 5/8" | 0.625 | 15.88 mm |
| 11/16" | 0.6875 | 17.46 mm |
| 3/4" | 0.750 | 19.05 mm |
| 13/16" | 0.8125 | 20.64 mm |
| 7/8" | 0.875 | 22.23 mm |
| 15/16" | 0.9375 | 23.81 mm |
| 1" | 1.000 | 25.40 mm |
Metric to SAE: quick reference
Working the other way? Here are the most-used metric sizes and their closest standard equivalent:
- 8 mm ≈ 5/16"
- 10 mm ≈ 3/8" (a hair larger)
- 13 mm ≈ 1/2"
- 17 mm ≈ 11/16"
- 19 mm ≈ 3/4"
Which SAE and metric sizes are interchangeable?
A few pairs are so close (within about 0.2 mm) that most people use them interchangeably for everyday jobs:
- 5/16" and 8 mm (0.06 mm apart)
- 7/16" and 11 mm (0.11 mm apart)
- 5/8" and 16 mm (0.12 mm apart)
- 3/4" and 19 mm (0.05 mm apart)
- 7/8" and 22 mm (0.23 mm apart)
- 15/16" and 24 mm (0.19 mm apart)
A word of caution: other pairs (like 1/2" and 13 mm, or 9/16" and 14 mm) are close but not exact. In a pinch they may work, but on tight or high-torque fasteners the slightly loose fit can round the corners. When in doubt, use the exact size from the chart above.
Frequently asked questions
What is 17 mm in standard? 17 mm is about 0.669 inches, closest to an 11/16" (0.6875") wrench.
Is 3/4" the same as 19 mm? Practically, yes — 3/4" is 19.05 mm, just 0.05 mm larger than 19 mm, so the two are interchangeable for almost any job.
What is 10 mm in SAE? 10 mm is about 0.394 inches, closest to 3/8" (0.375"), though 10 mm is slightly larger.
How do I convert inches to millimeters? Multiply the inch measurement by 25.4. For example, 1/2" = 0.5 x 25.4 = 12.7 mm.
Keep the chart on the wall
Tired of looking it up every time? Our Standard & Metric Conversion metal sign puts the everyday conversions right where you work — durable, rust-proof aluminum built for the garage, workshop, or shop. Made in Tomball, Texas.