Where do 32nds show up?

Machinist rules, tire-tread depth gauges, and drill charts between the letter sizes. A 32nd of an inch is just under 0.8 mm.

How big is 1/32 of an inch in millimetres?

1/32″ is exactly 0.79375 mm. Every mm value on this chart is exact, at 25.4 mm to the inch.

32nds of an inch

Thirty-two marks to the inch, each with its reduced name, exact decimal and exact millimetres.

32ths	Reduced	Decimal	mm
1/32	—	0.03125	0.79375
2/32	1/16	0.0625	1.5875
3/32	—	0.09375	2.38125
4/32	1/8	0.125	3.175
5/32	—	0.15625	3.96875
6/32	3/16	0.1875	4.7625
7/32	—	0.21875	5.55625
8/32	1/4	0.25	6.35
9/32	—	0.28125	7.14375
10/32	5/16	0.3125	7.9375
11/32	—	0.34375	8.73125
12/32	3/8	0.375	9.525
13/32	—	0.40625	10.31875
14/32	7/16	0.4375	11.1125
15/32	—	0.46875	11.90625
16/32	1/2	0.5	12.7

32ths	Reduced	Decimal	mm
17/32	—	0.53125	13.49375
18/32	9/16	0.5625	14.2875
19/32	—	0.59375	15.08125
20/32	5/8	0.625	15.875
21/32	—	0.65625	16.66875
22/32	11/16	0.6875	17.4625
23/32	—	0.71875	18.25625
24/32	3/4	0.75	19.05
25/32	—	0.78125	19.84375
26/32	13/16	0.8125	20.6375
27/32	—	0.84375	21.43125
28/32	7/8	0.875	22.225
29/32	—	0.90625	23.01875
30/32	15/16	0.9375	23.8125
31/32	—	0.96875	24.60625
32/32	1	1	25.4

Neighbouring rules: 16ths · 64ths · 128ths

Common questions

Where do 32nds show up?: Machinist rules, tire-tread depth gauges, and drill charts between the letter sizes. A 32nd of an inch is just under 0.8 mm.
How big is 1/32 of an inch in millimetres?: 1/32″ is exactly 0.79375 mm. Every mm value on this chart is exact, at 25.4 mm to the inch.

Where this comes from. Exact rational arithmetic on the values shown — fractions are pairs of integers until display, and inch–metric conversion uses 25.4 mm to the inch, exact by definition since 1959. See the full methodology.