19 mm spanner
19.00 mm · 0.75 in
19 mm across the flats · fits a M12 (DIN) hex head
The nearest imperial size
3/4″ is 19.05 mm — 0.05 mm larger than 19 mm.
That is close enough to be interchangeable. 0.05 mm is well inside the manufacturing tolerance of the fastener, and the two will feel identical in use.
The numbers
| Across flats | 19.00 mm · 0.75 in |
| Nearest imperial | 3/4″ — 19.05 mm |
| Difference | 0.05 mm — interchangeable |
| Fits | M12 (DIN) hex head |
Nearby metric sizes
| Size | mm | Nearest imperial | Gap |
|---|---|---|---|
| 16 mm | 16.00 | 5/8″ | 0.13 mm — swap |
| 17 mm | 17.00 | 11/16″ | 0.46 mm — do not |
| 18 mm | 18.00 | 11/16″ | 0.54 mm — do not |
| 19 mm | 19.00 | 3/4″ | 0.05 mm — swap |
| 21 mm | 21.00 | 13/16″ | 0.36 mm — do not |
| 22 mm | 22.00 | 7/8″ | 0.22 mm |
Frequently asked questions
What is 19 mm in inches?
0.75 inches. The nearest imperial spanner is 3/4″ at 19.05 mm, 0.05 mm larger.
Can I use 3/4″ instead of 19 mm?
Yes. They are 0.05 mm apart, which is inside the tolerance of the fastener itself — these two are interchangeable in practice and most mechanics never notice they own both.
What bolt does a 19 mm spanner fit?
A M12 (DIN) hex head. The full metric thread chart gives the tapping drill and clearance hole for it too.