Not to pick nits, but 3/16 of an inch is actually about 5 mm. Although most of us who prefer metric units to imperial probably are already used to doing the arithmetic, perhaps this rounded off chart will be handy to some readers.

1/16″ = 2 mm
1/8″ = 3 mm
3/16″ = 5 mm
1/4″ = 6 mm
5/16″ = 8 mm
3/8″ = 10 mm
7/16″ = 11 mm
1/2″ = 13 mm
9/16″ = 14 mm
5/8″ = 16 mm
11/16″ = 17 mm
3/4″ = 19 mm
13/16″ = 21 mm
7/8″ = 22 mm
15/16″ = 24 mm
1″ = 25 mm

If anyone’s interested, here’s one rounded to the nearest .5 mm

1/16″ = 1.5 mm
1/8″ = 3 mm
3/16″ = 5 mm
1/4″ = 6.5 mm
5/16″ = 8 mm
3/8″ = 9.5 mm
7/16″ = 11 mm
1/2″ = 12.5 mm
9/16″ = 14.5 mm
5/8″ = 16 mm
11/16″ = 17.5 mm
3/4″ = 19 mm
13/16″ = 20.5 mm
7/8″ = 22 mm
15/16″ = 24 mm
1″ = 25.5 mm