11/16″ spanner
17.46 mm · 0.69 in
11/16″ across the flats
The nearest metric size
17 mm is 17.00 mm — 0.46 mm smaller than 11/16″.
That is not close enough. 17 mm is smaller than the 11/16″ head, so it will not go on at all — which is the harmless failure of the two.
The numbers
| Across flats | 17.46 mm · 0.69 in |
| Nearest metric | 17 mm — 17.00 mm |
| Difference | 0.46 mm — not safe to substitute |
Nearby imperial sizes
| Size | mm | Nearest metric | Gap |
|---|---|---|---|
| 9/16″ | 14.29 | 14 mm | 0.29 mm — do not |
| 5/8″ | 15.88 | 16 mm | 0.13 mm — swap |
| 11/16″ | 17.46 | 17 mm | 0.46 mm — do not |
| 3/4″ | 19.05 | 19 mm | 0.05 mm — swap |
| 13/16″ | 20.64 | 21 mm | 0.36 mm — do not |
Frequently asked questions
What is 11/16″ in millimetres?
17.46 mm. The nearest metric spanner is 17 mm — 0.46 mm smaller.
Can I use 17 mm instead of 11/16″?
Not safely. The gap is 0.46 mm. 17 mm is smaller than 11/16″ and simply will not go on.
Where is 11/16″ used?
Imperial spanner sizes are "across flats" measurements and are still standard on American vehicles, plumbing and older machinery everywhere.