Inches to Millimeters (in to mm)


mm to inches (Swap Units)


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Inches to Millimeters formula

mm =
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More information: Inches
More information: Millimeters


Use of the inch can be traced back as far as the 7th century. The first explicit definition we could find of its length was after 1066 when it was defined as the length of three barleycorns. This was not a satisfactory reference as barleycorn lengths vary naturally. The British Standards Institute defined the inch as 25.4mm in 1930 in the document "Metric Units in Engineering: Going SI". In March 1932 the American Standards Association were asked to rule on whether to adopt the same value (at the time the American inch was 1/.03937 mm which approximated to 25.400051 mm). Because the values were so close, and because Britain has already settled on that value, the ASA adopted this value on March 13, 1933.


Inches to Millimeters formula

mm =


The millimetre is a unit of length in the metric system, equivalent to one thousandth of a metre (the SI base unit of length).

One meter was defined in 1983 by the 17th conference of weights and measures as “the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second” and the millimetre by definition is derived as being 1/1000th of that value.


Inches to Millimeters table

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Inches Millimeters
0in 0.00mm
1in 25.40mm
2in 50.80mm
3in 76.20mm
4in 101.60mm
5in 127.00mm
6in 152.40mm
7in 177.80mm
8in 203.20mm
9in 228.60mm
10in 254.00mm
11in 279.40mm
12in 304.80mm
13in 330.20mm
14in 355.60mm
15in 381.00mm
16in 406.40mm
17in 431.80mm
18in 457.20mm
19in 482.60mm
Inches Millimeters
20in 508.00mm
21in 533.40mm
22in 558.80mm
23in 584.20mm
24in 609.60mm
25in 635.00mm
26in 660.40mm
27in 685.80mm
28in 711.20mm
29in 736.60mm
30in 762.00mm
31in 787.40mm
32in 812.80mm
33in 838.20mm
34in 863.60mm
35in 889.00mm
36in 914.40mm
37in 939.80mm
38in 965.20mm
39in 990.60mm
Inches Millimeters
40in 1016.00mm
41in 1041.40mm
42in 1066.80mm
43in 1092.20mm
44in 1117.60mm
45in 1143.00mm
46in 1168.40mm
47in 1193.80mm
48in 1219.20mm
49in 1244.60mm
50in 1270.00mm
51in 1295.40mm
52in 1320.80mm
53in 1346.20mm
54in 1371.60mm
55in 1397.00mm
56in 1422.40mm
57in 1447.80mm
58in 1473.20mm
59in 1498.60mm