Decimal to Fraction Chart (Inch)

To convert a decimal inch to a fraction, multiply by 64 and round to the nearest whole number, then reduce: 0.375 × 64 = 24, so 24/64 = 3/8 in. One inch is 25.4 mm exactly, so 0.375 in = 9.525 mm. This chart lists every 1/64th from 1/64 to a full inch with its exact decimal and millimetre value.

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Reviewed

June 2, 2026

Machinists rarely call out an arbitrary decimal — work is dimensioned in halves, quarters, eighths, sixteenths, 32nds and 64ths, and 1/64 in (about 0.4 mm) is the finest fraction in common shop use. To round a measured decimal to the nearest fraction, multiply it by 64, round to the nearest whole number to get the count of 64ths, then divide that count by its greatest common factor with 64 to reduce. For example 0.123 × 64 = 7.87 → 8, giving 8/64 = 1/8 in.

Inch fractions, decimal inches and millimetres in 1/64 steps.

Fraction (in)

Decimal (in)

1/64

0.0156

0.3969

1/32

0.0313

0.7937

3/64

0.0469

1.1906

1/16

0.0625

1.5875

5/64

0.0781

1.9844

3/32

0.0938

2.3812

7/64

0.1094

2.7781

1/8

0.1250

3.1750

9/64

0.1406

3.5719

5/32

0.1563

3.9688

11/64

0.1719

4.3656

3/16

0.1875

4.7625

13/64

0.2031

5.1594

7/32

0.2188

5.5562

15/64

0.2344

5.9531

1/4

0.2500

6.3500

17/64

0.2656

6.7469

9/32

0.2813

7.1437

19/64

0.2969

7.5406

5/16

0.3125

7.9375

21/64

0.3281

8.3344

11/32

0.3438

8.7312

23/64

0.3594

9.1281

3/8

0.3750

9.5250

25/64

0.3906

9.9219

13/32

0.4063

10.3187

27/64

0.4219

10.7156

7/16

0.4375

11.1125

29/64

0.4531

11.5094

15/32

0.4688

11.9063

31/64

0.4844

12.3031

1/2

0.5000

12.7000

33/64

0.5156

13.0969

17/32

0.5313

13.4937

35/64

0.5469

13.8906

9/16

0.5625

14.2875

37/64

0.5781

14.6844

19/32

0.5938

15.0812

39/64

0.6094

15.4781

5/8

0.6250

15.8750

41/64

0.6406

16.2719

21/32

0.6563

16.6687

43/64

0.6719

17.0656

11/16

0.6875

17.4625

45/64

0.7031

17.8594

23/32

0.7188

18.2562

47/64

0.7344

18.6531

3/4

0.7500

19.0500

49/64

0.7656

19.4469

25/32

0.7813

19.8438

51/64

0.7969

20.2406

13/16

0.8125

20.6375

53/64

0.8281

21.0344

27/32

0.8438

21.4312

55/64

0.8594

21.8281

7/8

0.8750

22.2250

57/64

0.8906

22.6219

29/32

0.9063

23.0187

59/64

0.9219

23.4156

15/16

0.9375

23.8125

61/64

0.9531

24.2094

31/32

0.9688

24.6062

63/64

0.9844

25.0031

1.0000

25.4000