13 mm spanner
13.00 mm · 0.51 in
13 mm across the flats · fits a M8 hex head
The nearest imperial size
1/2″ is 12.70 mm — 0.30 mm smaller than 13 mm.
That is not close enough. 1/2″ is smaller than the 13 mm head, so it will not go on at all — which is the harmless failure of the two.
The numbers
| Across flats | 13.00 mm · 0.51 in |
| Nearest imperial | 1/2″ — 12.70 mm |
| Difference | 0.30 mm — not safe to substitute |
| Fits | M8 hex head |
Nearby metric sizes
| Size | mm | Nearest imperial | Gap |
|---|---|---|---|
| 10 mm | 10.00 | 3/8″ | 0.48 mm — do not |
| 11 mm | 11.00 | 7/16″ | 0.11 mm — swap |
| 12 mm | 12.00 | 1/2″ | 0.70 mm — do not |
| 13 mm | 13.00 | 1/2″ | 0.30 mm — do not |
| 14 mm | 14.00 | 9/16″ | 0.29 mm — do not |
| 15 mm | 15.00 | 9/16″ | 0.71 mm — do not |
| 16 mm | 16.00 | 5/8″ | 0.13 mm — swap |
Frequently asked questions
What is 13 mm in inches?
0.51 inches. The nearest imperial spanner is 1/2″ at 12.70 mm, 0.30 mm smaller.
Can I use 1/2″ instead of 13 mm?
Not safely. The gap is 0.30 mm. 1/2″ is smaller than 13 mm and simply will not go on.
What bolt does a 13 mm spanner fit?
A M8 hex head. The full metric thread chart gives the tapping drill and clearance hole for it too.