Fraction to Decimal Chart

All inch fractions in 64ths up to 1", reduced to lowest terms, with decimal-inch and millimetre equivalents. Machinists, carpenters, and drafters use this for drill selection, plan reading, and converting between fraction-drill and decimal/CAD measurements.

Inch fractions (1/64 → 1") — full table

Fraction (64ths)	Reduced	Decimal inch	Millimetres
1/64	—	0.015625	0.3969
2/64	1/32	0.031250	0.7937
3/64	—	0.046875	1.1906
4/64	1/16	0.062500	1.5875
5/64	—	0.078125	1.9844
6/64	3/32	0.093750	2.3812
7/64	—	0.109375	2.7781
8/64	1/8	0.125000	3.1750
9/64	—	0.140625	3.5719
10/64	5/32	0.156250	3.9688
11/64	—	0.171875	4.3656
12/64	3/16	0.187500	4.7625
13/64	—	0.203125	5.1594
14/64	7/32	0.218750	5.5562
15/64	—	0.234375	5.9531
16/64	1/4	0.250000	6.3500
17/64	—	0.265625	6.7469
18/64	9/32	0.281250	7.1437
19/64	—	0.296875	7.5406
20/64	5/16	0.312500	7.9375
21/64	—	0.328125	8.3344
22/64	11/32	0.343750	8.7312
23/64	—	0.359375	9.1281
24/64	3/8	0.375000	9.5250
25/64	—	0.390625	9.9219
26/64	13/32	0.406250	10.3187
27/64	—	0.421875	10.7156
28/64	7/16	0.437500	11.1125
29/64	—	0.453125	11.5094
30/64	15/32	0.468750	11.9062
31/64	—	0.484375	12.3031
32/64	1/2	0.500000	12.7000
33/64	—	0.515625	13.0969
34/64	17/32	0.531250	13.4937
35/64	—	0.546875	13.8906
36/64	9/16	0.562500	14.2875
37/64	—	0.578125	14.6844
38/64	19/32	0.593750	15.0812
39/64	—	0.609375	15.4781
40/64	5/8	0.625000	15.8750
41/64	—	0.640625	16.2719
42/64	21/32	0.656250	16.6687
43/64	—	0.671875	17.0656
44/64	11/16	0.687500	17.4625
45/64	—	0.703125	17.8594
46/64	23/32	0.718750	18.2562
47/64	—	0.734375	18.6531
48/64	3/4	0.750000	19.0500
49/64	—	0.765625	19.4469
50/64	25/32	0.781250	19.8438
51/64	—	0.796875	20.2406
52/64	13/16	0.812500	20.6375
53/64	—	0.828125	21.0344
54/64	27/32	0.843750	21.4312
55/64	—	0.859375	21.8281
56/64	7/8	0.875000	22.2250
57/64	—	0.890625	22.6219
58/64	29/32	0.906250	23.0187
59/64	—	0.921875	23.4156
60/64	15/16	0.937500	23.8125
61/64	—	0.953125	24.2094
62/64	31/32	0.968750	24.6062
63/64	—	0.984375	25.0031
64/64	1/1	1.000000	25.4000

Common shop fractions

Fraction	Decimal inch	mm
1/16	0.0625	1.5875
1/8	0.1250	3.1750
3/16	0.1875	4.7625
1/4	0.2500	6.3500
5/16	0.3125	7.9375
3/8	0.3750	9.5250
7/16	0.4375	11.1125
1/2	0.5000	12.7000
9/16	0.5625	14.2875
5/8	0.6250	15.8750
11/16	0.6875	17.4625
3/4	0.7500	19.0500
13/16	0.8125	20.6375
7/8	0.8750	22.2250
15/16	0.9375	23.8125
1	1.0000	25.4000

Decimal inch → mm (reverse look-up)

Decimal in	mm	Nearest fraction
0.010	0.2540	≈ 0 (thou)
0.031	0.7937	1/32
0.040	1.0160	≈ 3/64
0.050	1.2700	≈ 1/16 - 3/64
0.063	1.6002	1/16
0.100	2.5400	7/64 (.109)
0.125	3.1750	1/8
0.200	5.0800	13/64 (.203)
0.250	6.3500	1/4
0.375	9.5250	3/8
0.500	12.7000	1/2
0.625	15.8750	5/8
0.750	19.0500	3/4
0.875	22.2250	7/8
1.000	25.4000	1

Commonly rounded conversions

1 inch	= 25.4 mm (exact by international agreement, 1959)
1 foot	= 12 in = 304.8 mm
1 yard	= 36 in = 914.4 mm
1 mil / thou	= 0.001 in = 0.0254 mm = 25.4 µm
1 mm	≈ 0.03937 in = 39.37 thou
1 cm	= 0.3937 in
1 meter	≈ 39.3701 in = 3.2808 ft

Tips

To convert fraction → decimal: divide top by bottom. 5/16 = 5 ÷ 16 = 0.3125.
To convert decimal → fraction of an inch: multiply by 64, round to whole number, reduce. 0.42" × 64 = 26.88 → 27/64".
To convert inch → mm: multiply by 25.4. Exact — never rounded in engineering.
To convert mm → inch: multiply by 0.0393701 (or divide by 25.4). 15 mm ÷ 25.4 = 0.5906".
Never mix significant figures: if your measurement is to 1/64" (0.0156" = 0.4 mm), don't report a 0.001 mm result.
Shop rules of thumb: 1 mm ≈ 1/25 in or 40 mm ≈ 1-1/2 in for quick estimates.

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