Wrench Size Chart
Wrenches are sized to match the hex head of bolts and nuts. The chart below pairs each SAE (imperial) wrench size with its closest metric equivalent and shows the common fastener each size fits. This reference helps you quickly identify which wrench to grab for any job.
| SAE | Metric | Type | Common Fastener |
|---|---|---|---|
| 1/4" | 6 mm | combination | #10-24 bolts, small machine screws |
| 5/16" | 8 mm | combination | #10-32 bolts, small cap screws |
| 3/8" | 10 mm | combination | 1/4"-20 hex bolts |
| 7/16" | 11 mm | combination | 1/4"-28 fine thread bolts |
| 1/2" | 13 mm | combination | 5/16"-18 hex bolts |
| 9/16" | 14 mm | combination | 3/8"-16 hex bolts |
| 5/8" | 16 mm | combination | 3/8"-24 fine thread bolts |
| 11/16" | 17 mm | combination | 7/16"-14 hex bolts |
| 3/4" | 19 mm | combination | 1/2"-13 hex bolts, lug nuts |
| 13/16" | 21 mm | combination | 1/2"-20 fine thread, spark plugs |
| 7/8" | 22 mm | combination | 9/16"-12 hex bolts |
| 15/16" | 24 mm | combination | 5/8"-11 hex bolts |
| 1" | 25 mm | combination | 5/8"-18 fine thread bolts |
| 1-1/16" | 27 mm | combination | 3/4"-10 hex bolts |
| 1-1/8" | 29 mm | combination | 3/4"-16 fine thread bolts |
| 1-1/4" | 32 mm | combination | 7/8"-9 hex bolts, heavy equipment |
Wrench Selection Tips
Combination Wrenches
A combination wrench has an open end on one side and a box end (closed ring) on the other, both in the same size. The open end is faster for quick turns in accessible spaces, while the box end provides better grip and is less likely to slip on tight or corroded fasteners.
When to Use an Adjustable Wrench
Adjustable wrenches (Crescent wrenches) can fit multiple sizes but provide less grip than fixed-size wrenches. Use them only as a backup when the correct fixed-size wrench is unavailable. Always position the wrench so the pulling force is applied to the fixed jaw, not the adjustable jaw.
Avoiding Rounded Fasteners
Always use the correct size wrench. A wrench that is too large will slip and round the bolt head corners, making future removal difficult. If a bolt head is already rounded, use a bolt extractor socket or a pair of locking pliers (Vise-Grips) for removal.