Imperial standard
| Bolt Diameter | Head and Wrench Size | |
|---|---|---|
| Hex Bolt – Lag Bolt – Square Bolt | Heavy Hex Bolt | |
| #6 | 1/4″ | – |
| #8 | 1/4″ | – |
| #10 | 5/16″ | – |
| #12 | 5/16″ | – |
| 1/4″ | 7/16″ or 3/8″ | – |
| 5/16″ | 1/2″ | – |
| 3/8″ | 9/16″ | – |
| 7/16″ | 5/8″ | – |
| 1/2″ | 3/4″ | 7/8″ |
| 9/16″ | 13/16″ | – |
| 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″ | 1-3/4″ |
| 1-1/4″ | 1-7/8″ | 2″ |
Metric standard
| Bolt Diameter (mm) | Head/Wrench Size (mm) | |||
|---|---|---|---|---|
| ANSI/ISO | DIN | JIS | DIN/ISO Heavy Hex | |
| 4 | 7 | 7 | 7 | – |
| 5 | 8 | 8 | 8 | – |
| 6 | 10 | 10 | 10 | – |
| 7 | – | 11 | – | – |
| 8 | 13 | 13 | 12 | – |
| 10 | 16 | 17 | 14 | – |
| 12 | 18 | 19 | 17 | 22/21* |
| 14 | 21 | 22 | 19 | – |
| 16 | 24 | 24 | 22 | 27 |
| 18 | – | 27 | – | – |
| 20 | 30 | 30 | – | 34/32* |
| ANSI – American National Standards Institute ISO – International Organization for Standardisation DIN – Deutsches Institut für Normung JIS – Japanese Industrial Standard * Indicates ISO standard. | ||||