Millimeters to Inches Converter

How to convert millimeters to inches

inches = millimeters ÷ 25.4

1 millimeter is one thousandth of a meter (SI prefix milli, 10⁻³). 1 inch is exactly 25.4 millimeters.

Dividing by 25.4 is exact. Written as a multiplication the factor is a repeating decimal, 1 mm = 0.03937007874016… in, so a rounded multiplier such as 0.03937 is slightly off. This converter keeps the exact fraction (5/127) and rounds only the result it shows.

Worked example: 210 mm

1. Start with the value in millimeters: 210 mm.
2. Divide by 25.4, because 1 inch = 25.4 millimeters: 210 ÷ 25.4 = 8.267716535….
3. Round to the precision you need: 8.27 in to two decimals.
4. On a tape measure that is 8 1/4 in to the nearest 1/16.

Millimeters and inches side by side

Millimeters to inches chart

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Millimeters from 1 to 100 converted to inches with the exact factor, shown to five significant digits.

Millimeters to inches, part 1 of 4

mm	in	in, nearest 1/64
1	0.03937	3/64
2	0.07874	5/64
3	0.11811	1/8
4	0.15748	5/32
5	0.19685	13/64
6	0.23622	15/64
7	0.27559	9/32
8	0.31496	5/16
9	0.35433	23/64
10	0.3937	25/64
11	0.43307	7/16
12	0.47244	15/32
13	0.51181	33/64
14	0.55118	35/64
15	0.59055	19/32
16	0.62992	5/8
17	0.66929	43/64
18	0.70866	45/64
19	0.74803	3/4
20	0.7874	25/32
21	0.82677	53/64
22	0.86614	55/64
23	0.90551	29/32
24	0.94488	15/16
25	0.98425	63/64

Millimeters to inches, part 2 of 4

mm	in	in, nearest 1/64
26	1.0236	1 1/32
27	1.063	1 1/16
28	1.1024	1 7/64
29	1.1417	1 9/64
30	1.1811	1 3/16
31	1.2205	1 7/32
32	1.2598	1 17/64
33	1.2992	1 19/64
34	1.3386	1 11/32
35	1.378	1 3/8
36	1.4173	1 27/64
37	1.4567	1 29/64
38	1.4961	1 1/2
39	1.5354	1 17/32
40	1.5748	1 37/64
41	1.6142	1 39/64
42	1.6535	1 21/32
43	1.6929	1 11/16
44	1.7323	1 47/64
45	1.7717	1 49/64
46	1.811	1 13/16
47	1.8504	1 27/32
48	1.8898	1 57/64
49	1.9291	1 59/64
50	1.9685	1 31/32

Millimeters to inches, part 3 of 4

mm	in	in, nearest 1/64
51	2.0079	2 1/64
52	2.0472	2 3/64
53	2.0866	2 3/32
54	2.126	2 1/8
55	2.1654	2 11/64
56	2.2047	2 13/64
57	2.2441	2 1/4
58	2.2835	2 9/32
59	2.3228	2 21/64
60	2.3622	2 23/64
61	2.4016	2 13/32
62	2.4409	2 7/16
63	2.4803	2 31/64
64	2.5197	2 33/64
65	2.5591	2 9/16
66	2.5984	2 19/32
67	2.6378	2 41/64
68	2.6772	2 43/64
69	2.7165	2 23/32
70	2.7559	2 3/4
71	2.7953	2 51/64
72	2.8346	2 53/64
73	2.874	2 7/8
74	2.9134	2 29/32
75	2.9528	2 61/64

Millimeters to inches, part 4 of 4

mm	in	in, nearest 1/64
76	2.9921	2 63/64
77	3.0315	3 1/32
78	3.0709	3 5/64
79	3.1102	3 7/64
80	3.1496	3 5/32
81	3.189	3 3/16
82	3.2283	3 15/64
83	3.2677	3 17/64
84	3.3071	3 5/16
85	3.3465	3 11/32
86	3.3858	3 25/64
87	3.4252	3 27/64
88	3.4646	3 15/32
89	3.5039	3 1/2
90	3.5433	3 35/64
91	3.5827	3 37/64
92	3.622	3 5/8
93	3.6614	3 21/32
94	3.7008	3 45/64
95	3.7402	3 47/64
96	3.7795	3 25/32
97	3.8189	3 13/16
98	3.8583	3 55/64
99	3.8976	3 57/64
100	3.937	3 15/16

Fractions of an inch in decimals and millimeters

Every value is exact: 1 inch is 25.4 mm by definition.

Inch fractions in decimals and millimeters, part 1 of 2

Fraction	Decimal in	mm
1/64 in	0.015625	0.396875
1/32 in	0.03125	0.79375
3/64 in	0.046875	1.190625
1/16 in	0.0625	1.5875
5/64 in	0.078125	1.984375
3/32 in	0.09375	2.38125
7/64 in	0.109375	2.778125
1/8 in	0.125	3.175
9/64 in	0.140625	3.571875
5/32 in	0.15625	3.96875
11/64 in	0.171875	4.365625
3/16 in	0.1875	4.7625
13/64 in	0.203125	5.159375
7/32 in	0.21875	5.55625
15/64 in	0.234375	5.953125
1/4 in	0.25	6.35
17/64 in	0.265625	6.746875
9/32 in	0.28125	7.14375
19/64 in	0.296875	7.540625
5/16 in	0.3125	7.9375
21/64 in	0.328125	8.334375
11/32 in	0.34375	8.73125
23/64 in	0.359375	9.128125
3/8 in	0.375	9.525
25/64 in	0.390625	9.921875
13/32 in	0.40625	10.31875
27/64 in	0.421875	10.715625
7/16 in	0.4375	11.1125
29/64 in	0.453125	11.509375
15/32 in	0.46875	11.90625
31/64 in	0.484375	12.303125
1/2 in	0.5	12.7

Inch fractions in decimals and millimeters, part 2 of 2

Fraction	Decimal in	mm
33/64 in	0.515625	13.096875
17/32 in	0.53125	13.49375
35/64 in	0.546875	13.890625
9/16 in	0.5625	14.2875
37/64 in	0.578125	14.684375
19/32 in	0.59375	15.08125
39/64 in	0.609375	15.478125
5/8 in	0.625	15.875
41/64 in	0.640625	16.271875
21/32 in	0.65625	16.66875
43/64 in	0.671875	17.065625
11/16 in	0.6875	17.4625
45/64 in	0.703125	17.859375
23/32 in	0.71875	18.25625
47/64 in	0.734375	18.653125
3/4 in	0.75	19.05
49/64 in	0.765625	19.446875
25/32 in	0.78125	19.84375
51/64 in	0.796875	20.240625
13/16 in	0.8125	20.6375
53/64 in	0.828125	21.034375
27/32 in	0.84375	21.43125
55/64 in	0.859375	21.828125
7/8 in	0.875	22.225
57/64 in	0.890625	22.621875
29/32 in	0.90625	23.01875
59/64 in	0.921875	23.415625
15/16 in	0.9375	23.8125
61/64 in	0.953125	24.209375
31/32 in	0.96875	24.60625
63/64 in	0.984375	25.003125
1 in	1	25.4

inches = millimeters ÷ 25.4. Factors: NIST SP 811, NIST Handbook 44, BIPM SI Brochure. unitcheck.net/length/millimeters-to-inches/

Common values

Metric and inch sizes rarely match

Because 25.4 has no simple common factor with the usual inch fractions, a round metric size almost never equals a round inch size. 6 mm is 0.2362 in, close to but not the same as 1/4 in (6.35 mm). When a part has to fit, compare the decimal values and the error shown next to the fraction instead of the nearest named size.

Going the other way? Use the Inches to Millimeters converter.