Inch to Millimetre Chart: 1/64 in to 100 mm

One inch is exactly 25.4 millimetres. The two tables below convert in both directions: fractional inches to millimetres, and millimetres to inches.

Inch ruler marked in sixteenths with millimetre equivalents
Every sixteenth of an inch with its millimetre equivalent. The scale is linear because the conversion is a single multiplication.

Inch fractions to millimetres

Sixty-fourths of an inch from 1/64 up to 1 inch. Fractions are shown reduced, as they appear on a drawing.

Fraction (in)Decimal (in)Millimetres
1/640.0156250.3969
1/320.0312500.7937
3/640.0468751.1906
1/160.0625001.5875
5/640.0781251.9844
3/320.0937502.3812
7/640.1093752.7781
1/80.1250003.1750
9/640.1406253.5719
5/320.1562503.9688
11/640.1718754.3656
3/160.1875004.7625
13/640.2031255.1594
7/320.2187505.5562
15/640.2343755.9531
1/40.2500006.3500
17/640.2656256.7469
9/320.2812507.1437
19/640.2968757.5406
5/160.3125007.9375
21/640.3281258.3344
11/320.3437508.7312
23/640.3593759.1281
3/80.3750009.5250
25/640.3906259.9219
13/320.40625010.3187
27/640.42187510.7156
7/160.43750011.1125
29/640.45312511.5094
15/320.46875011.9062
31/640.48437512.3031
1/20.50000012.7000
33/640.51562513.0969
17/320.53125013.4937
35/640.54687513.8906
9/160.56250014.2875
37/640.57812514.6844
19/320.59375015.0812
39/640.60937515.4781
5/80.62500015.8750
41/640.64062516.2719
21/320.65625016.6687
43/640.67187517.0656
11/160.68750017.4625
45/640.70312517.8594
23/320.71875018.2562
47/640.73437518.6531
3/40.75000019.0500
49/640.76562519.4469
25/320.78125019.8438
51/640.79687520.2406
13/160.81250020.6375
53/640.82812521.0344
27/320.84375021.4312
55/640.85937521.8281
7/80.87500022.2250
57/640.89062522.6219
29/320.90625023.0187
59/640.92187523.4156
15/160.93750023.8125
61/640.95312524.2094
31/320.96875024.6062
63/640.98437525.0031
11.00000025.4000

Millimetres to inches

Half-millimetre steps from 0.5 mm to 100 mm. The third column gives the value in sixty-fourths, which is the nearest usable fraction on an inch rule.

MillimetresInchesSixty-fourths
0.50.019691.26
10.039372.52
1.50.059063.78
20.078745.04
2.50.098436.30
30.118117.56
3.50.137808.82
40.1574810.08
4.50.1771711.34
50.1968512.60
5.50.2165413.86
60.2362215.12
6.50.2559116.38
70.2755917.64
7.50.2952818.90
80.3149620.16
8.50.3346521.42
90.3543322.68
9.50.3740223.94
100.3937025.20
10.50.4133926.46
110.4330727.72
11.50.4527628.98
120.4724430.24
12.50.4921331.50
130.5118132.76
13.50.5315034.02
140.5511835.28
14.50.5708736.54
150.5905537.80
15.50.6102439.06
160.6299240.31
16.50.6496141.57
170.6692942.83
17.50.6889844.09
180.7086645.35
18.50.7283546.61
190.7480347.87
19.50.7677249.13
200.7874050.39
20.50.8070951.65
210.8267752.91
21.50.8464654.17
220.8661455.43
22.50.8858356.69
230.9055157.95
23.50.9252059.21
240.9448860.47
24.50.9645761.73
250.9842562.99
25.51.0039464.25
261.0236265.51
26.51.0433166.77
271.0629968.03
27.51.0826869.29
281.1023670.55
28.51.1220571.81
291.1417373.07
29.51.1614274.33
301.1811075.59
30.51.2007976.85
311.2204778.11
31.51.2401679.37
321.2598480.63
32.51.2795381.89
331.2992183.15
33.51.3189084.41
341.3385885.67
34.51.3582786.93
351.3779588.19
35.51.3976489.45
361.4173290.71
36.51.4370191.97
371.4566993.23
37.51.4763894.49
381.4960695.75
38.51.5157597.01
391.5354398.27
39.51.5551299.53
401.57480100.79
40.51.59449102.05
411.61417103.31
41.51.63386104.57
421.65354105.83
42.51.67323107.09
431.69291108.35
43.51.71260109.61
441.73228110.87
44.51.75197112.13
451.77165113.39
45.51.79134114.65
461.81102115.91
46.51.83071117.17
471.85039118.43
47.51.87008119.69
481.88976120.94
48.51.90945122.20
491.92913123.46
49.51.94882124.72
501.96850125.98
50.51.98819127.24
512.00787128.50
51.52.02756129.76
522.04724131.02
52.52.06693132.28
532.08661133.54
53.52.10630134.80
542.12598136.06
54.52.14567137.32
552.16535138.58
55.52.18504139.84
562.20472141.10
56.52.22441142.36
572.24409143.62
57.52.26378144.88
582.28346146.14
58.52.30315147.40
592.32283148.66
59.52.34252149.92
602.36220151.18
60.52.38189152.44
612.40157153.70
61.52.42126154.96
622.44094156.22
62.52.46063157.48
632.48031158.74
63.52.50000160.00
642.51969161.26
64.52.53937162.52
652.55906163.78
65.52.57874165.04
662.59843166.30
66.52.61811167.56
672.63780168.82
67.52.65748170.08
682.67717171.34
68.52.69685172.60
692.71654173.86
69.52.73622175.12
702.75591176.38
70.52.77559177.64
712.79528178.90
71.52.81496180.16
722.83465181.42
72.52.85433182.68
732.87402183.94
73.52.89370185.20
742.91339186.46
74.52.93307187.72
752.95276188.98
75.52.97244190.24
762.99213191.50
76.53.01181192.76
773.03150194.02
77.53.05118195.28
783.07087196.54
78.53.09055197.80
793.11024199.06
79.53.12992200.31
803.14961201.57
80.53.16929202.83
813.18898204.09
81.53.20866205.35
823.22835206.61
82.53.24803207.87
833.26772209.13
83.53.28740210.39
843.30709211.65
84.53.32677212.91
853.34646214.17
85.53.36614215.43
863.38583216.69
86.53.40551217.95
873.42520219.21
87.53.44488220.47
883.46457221.73
88.53.48425222.99
893.50394224.25
89.53.52362225.51
903.54331226.77
90.53.56299228.03
913.58268229.29
91.53.60236230.55
923.62205231.81
92.53.64173233.07
933.66142234.33
93.53.68110235.59
943.70079236.85
94.53.72047238.11
953.74016239.37
95.53.75984240.63
963.77953241.89
96.53.79921243.15
973.81890244.41
97.53.83858245.67
983.85827246.93
98.53.87795248.19
993.89764249.45
99.53.91732250.71
1003.93701251.97

Common questions

How many millimetres are in one inch?

Exactly 25.4. The inch has been defined as 25.4 millimetres since the 1959 international yard and pound agreement, so the conversion is exact rather than rounded.

What is 1/4 inch in millimetres?

1/4 inch is 6.3500 mm. Half of that, 1/8 inch, is 3.1750 mm, and 3/4 inch is 19.0500 mm.

How do I convert millimetres back to inches?

Divide by 25.4. For example 10 mm divided by 25.4 is 0.39370 inch, which is just under 13/32 inch.

Why do drawings mix fractions and decimals?

Fractional inches are used for stock sizes such as 1/2 inch plate, while decimals are used for tolerances and for anything measured with a vernier or micrometer. The table above bridges the two.