7 CFR § 51.653 - Metric conversion table.

Inches	Millimeters (mm)
1/4 equals	6.4
3/8 equals	9.5
1/2 equals	12.7
9/16 equals	14.3
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
1 1/2 equals	38.1
3 equals	76.2
3 2/16 equals	79.4
3 6/16 equals	85.7
3 8/16 equals	88.9
3 10/16 equals	92.1
3 13/16 equals	96.8
3 14/16 equals	98.4
3 15/16 equals	100.0
4 2/16 equals	104.8
4 5/16 equals	109.5
4 8/16 equals	114.3
4 12/16 equals	120.7
5 equals	127.0