27 mm spanner
27.00 mm · 1.06 in
27 mm across the flats
The nearest imperial size
1-1/16″ is 26.99 mm — 0.01 mm smaller than 27 mm.
That is close enough to be interchangeable. 0.01 mm is well inside the manufacturing tolerance of the fastener, and the two will feel identical in use.
The numbers
| Across flats | 27.00 mm · 1.06 in |
| Nearest imperial | 1-1/16″ — 26.99 mm |
| Difference | 0.01 mm — interchangeable |
Nearby metric sizes
| Size | mm | Nearest imperial | Gap |
|---|---|---|---|
| 24 mm | 24.00 | 15/16″ | 0.19 mm |
| 27 mm | 27.00 | 1-1/16″ | 0.01 mm — swap |
| 30 mm | 30.00 | 1-1/8″ | 1.43 mm — do not |
Frequently asked questions
What is 27 mm in inches?
1.06 inches. The nearest imperial spanner is 1-1/16″ at 26.99 mm, 0.01 mm smaller.
Can I use 1-1/16″ instead of 27 mm?
Yes. They are 0.01 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.
Where is 27 mm used?
This size sits between the standard hex head sizes rather than on one, so it turns up on proprietary fasteners, plumbing fittings and older machinery rather than on ordinary bolts.