30 mm spanner
30.00 mm · 1.18 in
30 mm across the flats · fits a M20 hex head
The nearest imperial size
1-1/8″ is 28.57 mm — 1.43 mm smaller than 30 mm.
That is not close enough. 1-1/8″ is smaller than the 30 mm head, so it will not go on at all — which is the harmless failure of the two.
The numbers
| Across flats | 30.00 mm · 1.18 in |
| Nearest imperial | 1-1/8″ — 28.57 mm |
| Difference | 1.43 mm — not safe to substitute |
| Fits | M20 hex head |
Nearby metric sizes
| Size | mm | Nearest imperial | Gap |
|---|---|---|---|
| 27 mm | 27.00 | 1-1/16″ | 0.01 mm — swap |
| 30 mm | 30.00 | 1-1/8″ | 1.43 mm — do not |
| 32 mm | 32.00 | 1-1/8″ | 3.43 mm — do not |
Frequently asked questions
What is 30 mm in inches?
1.18 inches. The nearest imperial spanner is 1-1/8″ at 28.57 mm, 1.43 mm smaller.
Can I use 1-1/8″ instead of 30 mm?
Not safely. The gap is 1.43 mm. 1-1/8″ is smaller than 30 mm and simply will not go on.
What bolt does a 30 mm spanner fit?
A M20 hex head. The full metric thread chart gives the tapping drill and clearance hole for it too.