Utility Loft → Socket Size Converter
Socket & Wrench Size Converter
Convert metric (mm) to SAE (inch) and back for sockets and wrenches — with the closest matching size and how tight the fit really is.
Enter a metric size above to find the closest SAE (inch) wrench.
Tip: a loose socket can round off a fastener under torque — match within ~0.2 mm for tight jobs.
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Master wrench conversion chart
Every standard size from both systems, sorted by physical width, with the closest match in the other system.
| Size | System | Width (mm) | Closest other | Fit |
|---|---|---|---|---|
| 5/32" | SAE | 3.97 | 4 mm | ≈ exact |
| 4 mm | Metric | 4.00 | 5/32" | ≈ exact |
| 4.5 mm | Metric | 4.50 | 3/16" | close |
| 3/16" | SAE | 4.76 | 5 mm | close |
| 5 mm | Metric | 5.00 | 3/16" | close |
| 5.5 mm | Metric | 5.50 | 7/32" | ≈ exact |
| 7/32" | SAE | 5.56 | 5.5 mm | ≈ exact |
| 6 mm | Metric | 6.00 | 1/4" | close |
| 1/4" | SAE | 6.35 | 6 mm | close |
| 7 mm | Metric | 7.00 | 9/32" | ≈ exact |
| 9/32" | SAE | 7.14 | 7 mm | ≈ exact |
| 5/16" | SAE | 7.94 | 8 mm | ≈ exact |
| 8 mm | Metric | 8.00 | 5/16" | ≈ exact |
| 11/32" | SAE | 8.73 | 9 mm | close |
| 9 mm | Metric | 9.00 | 11/32" | close |
| 3/8" | SAE | 9.53 | 10 mm | loose |
| 10 mm | Metric | 10.00 | 3/8" | loose |
| 11 mm | Metric | 11.00 | 7/16" | ≈ exact |
| 7/16" | SAE | 11.11 | 11 mm | ≈ exact |
| 12 mm | Metric | 12.00 | 1/2" | loose |
| 1/2" | SAE | 12.70 | 13 mm | close |
| 13 mm | Metric | 13.00 | 1/2" | close |
| 14 mm | Metric | 14.00 | 9/16" | close |
| 9/16" | SAE | 14.29 | 14 mm | close |
| 15 mm | Metric | 15.00 | 9/16" | loose |
| 5/8" | SAE | 15.88 | 16 mm | ≈ exact |
| 16 mm | Metric | 16.00 | 5/8" | ≈ exact |
| 17 mm | Metric | 17.00 | 11/16" | loose |
| 11/16" | SAE | 17.46 | 17 mm | loose |
| 18 mm | Metric | 18.00 | 11/16" | loose |
| 19 mm | Metric | 19.00 | 3/4" | ≈ exact |
| 3/4" | SAE | 19.05 | 19 mm | ≈ exact |
| 20 mm | Metric | 20.00 | 13/16" | loose |
| 13/16" | SAE | 20.64 | 21 mm | close |
| 21 mm | Metric | 21.00 | 13/16" | close |
| 22 mm | Metric | 22.00 | 7/8" | close |
| 7/8" | SAE | 22.23 | 22 mm | close |
| 15/16" | SAE | 23.81 | 24 mm | ≈ exact |
| 24 mm | Metric | 24.00 | 15/16" | ≈ exact |
| 1" | SAE | 25.40 | 24 mm | loose |
| 1-1/16" | SAE | 26.99 | 27 mm | ≈ exact |
| 27 mm | Metric | 27.00 | 1-1/16" | ≈ exact |
| 1-1/8" | SAE | 28.58 | 30 mm | loose |
| 30 mm | Metric | 30.00 | 1-1/8" | loose |
| 1-1/4" | SAE | 31.75 | 32 mm | close |
| 32 mm | Metric | 32.00 | 1-1/4" | close |
Widths are across-flats. "≈ exact" ≈ within 0.2 mm; "loose" pairings can slip under torque — use the correct-system tool for tight fasteners.
Frequently asked questions
What is 10mm in standard (SAE)?
A 10 mm socket is closest to 3/8 inch (9.53 mm) — a hair larger, so it's a usable but slightly loose fit. There's no exact SAE equivalent to 10 mm, which is why a dedicated 10 mm is the socket everyone loses.
What is 1/2 inch in metric?
A 1/2-inch socket is 12.7 mm, closest to a 13 mm (a near fit) — 13 mm is 0.3 mm larger. A 12 mm would be too small.
Can I use an SAE socket on a metric bolt?
Sometimes, when the sizes are within about 0.2 mm — like 3/4 inch and 19 mm, which are almost identical. But a loose socket can round off the corners of a fastener under torque, so for anything tight, use the correct-system socket. The chart flags near-exact versus loose pairings.
Which SAE and metric sizes are interchangeable?
The closest matches are 3/4" ≈ 19 mm, 7/16" ≈ 11 mm, 5/16" ≈ 8 mm, and 3/8" ≈ 10 mm (looser). These are close enough for light use but never ideal for high torque. Enter any size in the converter to see how tight the match is.
Why do some sizes have no good equivalent?
SAE and metric are independent systems, so many sizes fall between the other's steps — 10 mm and 1/2 inch are classic examples with no exact partner. That's why a mixed toolbox needs both sets.