Wrench & Socket Size Chart
Know the wrench size but not the bolt size? Find the possible bolt diameter using the charts below. Wrench dimensions are nominal across the flats.
Tip: Use Ctrl+F on a computer to find a wrench size, such as 9/16 or 17 mm. On a phone, use your browser’s Find in Page feature.
SAE Hex Bolts
Common SAE finished hex-head bolt sizes, with heavy-hex sizes for comparison.
| Bolt diameter | Standard hex wrench | Heavy hex wrench |
|---|---|---|
| 1/4" | 7/16" | 1/2" |
| 5/16" | 1/2" | 9/16" |
| 3/8" | 9/16" | 11/16" |
| 7/16" | 5/8" | 3/4" |
| 1/2" | 3/4" | 7/8" |
| 9/16" | 13/16" | 15/16" |
| 5/8" | 15/16" | 1-1/16" |
| 3/4" | 1-1/8" | 1-1/4" |
| 7/8" | 1-5/16" | 1-7/16" |
| 1" | 1-1/2" | 1-5/8" |
| 1-1/8" | 1-11/16" | 1-13/16" |
| 1-1/4" | 1-7/8" | 2" |
| 1-3/8" | 2-1/16" | 2-3/16" |
| 1-1/2" | 2-1/4" | 2-3/8" |
Metric Hex Bolts
DIN 931/933 hex sizes are shown first because they are the common Crowbar’s stocked style. ISO 4014/4017 sizes are included for comparison. Confirm the actual head before choosing a wrench.
| Bolt diameter | DIN hex wrench (stocked) | ISO hex wrench (comparison) |
|---|---|---|
| M5 | 8 mm | 8 mm |
| M6 | 10 mm | 10 mm |
| M8 | 13 mm | 13 mm |
| M10 | 17 mm | 16 mm |
| M12 | 19 mm | 18 mm |
| M14 | 22 mm | 21 mm |
| M16 | 24 mm | 24 mm |
| M18 | 27 mm | 27 mm |
| M20 | 30 mm | 30 mm |
| M22 | 32 mm | 34 mm |
| M24 | 36 mm | 36 mm |
| M27 | 41 mm | 41 mm |
| M30 | 46 mm | 46 mm |
Allen / Socket Head
Typical hex socket sizes for standard socket-head cap screws (not button-head or flat-head screws).
| Bolt diameter | Socket / Allen key | System |
|---|---|---|
| #4 | 3/32" | SAE |
| #6 | 7/64" | SAE |
| #8 | 9/64" | SAE |
| #10 | 5/32" | SAE |
| 1/4" | 3/16" | SAE |
| 5/16" | 1/4" | SAE |
| 3/8" | 5/16" | SAE |
| 1/2" | 3/8" | SAE |
| 5/8" | 1/2" | SAE |
| 3/4" | 5/8" | SAE |
| M3 | 2.5 mm | Metric |
| M4 | 3 mm | Metric |
| M5 | 4 mm | Metric |
| M6 | 5 mm | Metric |
| M8 | 6 mm | Metric |
| M10 | 8 mm | Metric |
| M12 | 10 mm | Metric |
| M14 | 12 mm | Metric |
| M16 | 14 mm | Metric |
Important: Wrench size alone cannot positively identify a bolt. Heavy hex, flange bolts, DIN/ISO variations and other head styles may differ. Verify thread diameter and pitch before replacing a fastener.