7 CFR § 51.714 - Metric conversion table.

Inches	Millimeters (mm)
1/4 equals	6.4
5/16 equals	7.9
3/8 equals	9.5
1/2 equals	12.7
5/8 equals	15.9
3/4 equals	19.1
7/8 equals	22.2
1 equals	25.4
1 1/4 equals	31.8
2 3/16 equals	55.6
2 4/16 equals	57.2
2 7/16 equals	61.9
2 8/16 equals	63.5
2 9/16 equals	65.1
2 11/16 equals	68.3
2 12/16 equals	69.9
2 15/16 equals	74.6
3 1/16 equals	77.8
3 3/16 equals	81.0
3 5/16 equals	84.1
3 7/16 equals	87.3
3 9/16 equals	90.5
3 13/16 equals	96.8