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Metric - Imperial Conversions   

 

Size(mm) 

Size(in)

Fraction(inch)

Letter or Number

Description

0.2

0.0079

 

 

 

0.22

0.0087

 

 

 

0.25

0.0098

 

 

 

0.28

0.0110

 

 

 

0.3

0.0118

 

 

 

0.32

0.0126

 

 

 

0.35

0.0138

 

80

 

0.38

0.0150

 

79

 

0.39

0.0156

1/64

 

 

0.4

0.0157

 

78

 

0.42

0.0165

 

 

 

0.45

0.0177

 

77

 

0.48

0.0189

 

 

 

0.5

0.0197

 

76

 

0.52

0.0205

 

75

 

0.55

0.0217

 

 

 

0.58

0.0228

 

74

 

0.6

0.0236

 

73

Tapping Drill 16 BA

0.62

0.0244

 

72

 

0.65

0.0256

 

71

 

0.68

0.0268

 

 

 

0.7

0.0276

 

70

Tapping Drill 15 BA

0.72

0.0283

 

 

 

0.75

0.0295

 

69

Tapping Drill ISO metric coarse 1 mm

0.78

0.0307

 

 

 

0.79

0.0312

1/32

68

 

0.8

0.0315

 

 

Tapping Drill 14 BA

0.82

0.0323

 

67

 

0.85

0.0335

 

66

Tapping Drill ISO Metric Coarse 1.1 mm

0.88

0.0346

 

 

 

0.9

0.0354

 

65

 

0.92

0.0362

 

64

 

0.95

0.0374

 

63

Tapping Drill ISO Metric Coarse 1.2 mm

0.98

0.0386

 

62

Tapping Drill 13 BA

1

0.0394

 

61

Tapping Drill 12 BA and 17swg CEI

1.05

0.0413

 

60

Tapping Drill 12 BA

1.1

0.0433

 

59

Tapping Dnll ISO Metric Coarse 1.4 mm

1.15

0.0453

 

58

 

1.19

0.0469

3/64

57

Tapping Drill 16swg CEI

1.2

0.0472

 

56

Tapping Drill 11 BA and 1/16 Whitworth

1.25

0.0492

 

 

Tapping Dnll ISO Metric Coarse 1.6 mm and No 0 UNF

1.3

0.0512

 

55

 

1.35

0.0531

 

 

Tapping Drill ISO Metric Special Pitches 1.7 mm

1.4

0.0551

 

54

Tapping Drill 15swg CEI  and 10BA

1.45

0.0571

 

 

Tapping Drill ISO Metric Coarse 1.8 mm

1.5

0.0591

 

53

Tapping Drill 9 BA

1.55

0.0610

 

 

Tapping Drill ISO Metric Special Pitches 2 mm and No1 UNC

1.58

0.0625

1/16

 

 

1.6

0.0630

 

52

Tapping Drill ISO Metric Coarse 2 mm, No1 UNF and 14swg CEI

1.65

0.0650

 

 

 

1.7

0.0669

 

51

 

1.75

0.0689

 

 

Tapping Drill ISO Metric Coarse 2.2 mm

1.8

0.0709

 

50

Tapping Drill 8 BA

1.85

0.0728

 

49

Tapping Drill 3/32 Whitworth, No2 UNC and 13swg CEI

1.9

0.0748

 

48

Tapping Drill  ISO Metric Special Pitches 2.3 mm and No2 UNF

1.95

0.0768

 

 

 

1.98

0.0781

5/64

 

 

2

0.0787

 

47

Tapping Drill 7 BA

2.05

0.0807

 

46

Tapping Drill ISO Metric Coarse 2.5 mm and 12swg CEI

2.1

0.0827

 

45

Tapping Drill No3 UNC

2.15

0.0846

 

 

Tapping Drill  ISO Metric Special Pitches 2.6 mm and No3 UNF

2.2

0.0866

 

44

 

2.25

0.0886

 

43

 

2.3

0.0906

 

 

Tapping Drill 6 BA

2.35

0.0925

 

 

Tapping Drill No4 UNC

2.38

0.0938

3/32

42

 

2.4

0.0945

 

 

Tapping Drill  ISO Metric Special Pitches 3 mm and No4 UNF

2.45

0.0965

 

41

 

2.5

0.0984

 

40

Tapping Drill ISO Metric Coarse 3 mm

2.55

0.1004

 

39

Tapping Drill 1/8 Whitworth 1/8 BSC and 1/8 CEI

2.6

0.1024

 

38

Tapping Drill 5 BA

2.65

0.1043

 

37

Tapping Drill ISO Metric Fine 3 mm and No5 UNC

2.7

0.1063

 

36

Tapping Drill No5 UNF

2.75

0.1083

 

 

 

2.78

0.1094

7/64

 

 

2.8

0.1102

 

35

 

2.85

0.1122

 

34

Tapping Drill No6 UNC

2.9

0.1142

 

33

Tapping Drill ISO Metric Coarse 3.5 mm

2.95

0.1161

 

32

Tapping Drill 4 BA and No6 UNF

3

0.1181

 

31

 

3.1

0.1220

 

 

 

3.18

0.1250

1/8

 

 

3.2

0.1260

 

30

Tapping Drill 5/32 BSC, 5/32 WW, ISO Metric Special Pitches 2.3mm & 0.154 CEI

3.3

0.1299

 

 

Tapping Drill ISO Metric Coarse 4 mm

3.4

0.1339

 

29

Tapping Drill 3 BA

3.5

0.1378

 

 

Tapping Drill ISO Metric Fine 4 mm and No8 UNC

3.55

0.1398

 

 

Tapping Drill No8 UNF

3.57

0.1406

9/64

28

 

3.6

0.1417

 

27

Tapping Drill 0.175 CEI

3.7

0.1457

 

26

Tapping Drill 3/16 Whitworth

3.8

0.1496

 

25

Tapping Drill ISO Metric Coarse 4.5 mm

3.9

0.1535

 

24

Tapping Drill No10 UNC

3.97

0.1562

5/32

23

Tapping Drill 3/16 BSF 3/16 CEI and 3/16 BSC

4

0.1575

 

22

Tapping Drill 2 BA

4.1

0.1614

 

21

Tapping Drill  ISO Metric Special Pitches 5 mm and No 10 UNF

4.2

0.1654

 

20

Tapping Drill ISO Metric Coarse 5 mm

4.3

0.1693

 

19

 

4.37

0.1719

11/64

18

 

4.4

0.1732

 

17

 

4.5

0.1772

 

16

Tapping Drill 1 BA, 7/32 Whitworth, and ISO Metric Fine 5 mm

4.55

0.1791

 

 

Tapping Drill No12 UNC

4.6

0.1811

 

15

Tapping Drill 7/32 BSF and ISO Metric Special Pitches 5.5 mm

4.65

0.1831

 

 

Tapping Drill  No 12 UNF

4.7

0.1850

 

14

 

4.76

0.1875

3/16

13

 

4.8

0.1890

 

12

 

4.9

0.1929

 

11

 

5

0.1969

 

10

Tapping Drill ISO Metric Coarse 6 mm

5.1

0.2008

 

9

Tapping Drill 0 BA and 1/4 Whitworth

5.16

0.2031

13/64

8

 

5.2

0.2047

 

7

Tapping Drill 1/4 UNC and ISO Metric Fine 6 mm

5.3

0.2087

 

6

Tapping Drill 1/4 BSF

5.4

0.2126

 

5

 

5.5

0.2165

 

4

Tapping Drill 1/4 UNF

5.56

0.2188

7/32

3

Tapping Drill 1/4 BSC and 1/4 CEI

5.6

0.2205

 

2

 

5.7

0.2244

 

 

 

5.8

0.2283

 

1

Tapping Drill 0.266 CEI

5.9

0.2323

 

A

 

5.95

0.2344

15/64

 

 

6

0.2362

 

B

Tapping Drill ISO Metric Coarse 7 mm and 9/32 BSF

6.1

0.2402

 

C

 

6.2

0.2441

 

D

Tapping Drill 9/32 BSC, 0.281 CEI and ISO Metric Fine 7 mm

6.3

0.2480

 

E

 

6.35

0.2500

1/4

 

 

6.4

0.2520

 

 

Tapping Drill 1/16 BSTP

6.5

0.2559

 

F

Tapping Drill 5/16 Whitworth

6.6

0.2598

 

G

Tapping Drill 5/16 UNC and 1/16 BSP

6.7

0.2638

 

H

 

6.75

0.2655

17/64

 

Tapping Drill 5/16 BSF

6.8

0.2677

 

 

Tapping Drill ISO Metric Coarse 8 mm

6.9

0.2717

 

I

Tapping Drill 5/16 UNF

7

0.2756

 

J

Tapping Drill 5/16 BSC, ISO Metric Fine 8 mm and 5/16 CEI

7.1

0.2795

 

K

 

7.14

0.2812

9/32

 

 

7.2

0.2835

 

 

Tapping Drill ISO Metric Special Pitches 8 mm

7.3

0.2874

 

L

 

7.4

0.2913

 

M

 

7.5

0.2953

 

 

 

7.54

0.2969

19/64

 

 

7.6

0.2992

 

N

 

7.7

0.3031

 

 

 

7.8

0.3071

 

 

Tapping Dnll ISO Metric Coarse 9 mm

7.9

0.3110

 

 

 

7.94

0.3125

5/16

 

Tapping Drill 3/8 Whitworth

8

0.3150

 

0

Tapping Drill 3/8 UNC and ISO Metric Special Pitches 9 mm

8.1

0.3189

 

 

 

8.2

0.3228

 

P

Tapping Drill 3/8 BSF

8.3

0.3268

 

 

 

8.33

0.3281

21/64

 

 

8.4

0.3307

 

Q

Tapping Drill 1/8 BSTP

8.5

0.3346

 

 

Tapping Drill ISO Metric Coarse 10 mm and 3/8 UNF

8.6

0.3386

 

R

Tapping Drill 3/8 BSC and 3/8 CEI

8.7

0.3425

 

 

 

8.73

0.3438

11/32

 

Tapping Drill 1/8 BSP

8.8

0.3465

 

5

Tapping Drill ISO Metric Fine 10 mm

8.9

0.3504

 

 

 

9

0.3543

 

 

Tapping Drill ISO Metric Special Pitches 10 mm

9.1

0.3583

 

T

 

9.13

0.3594

23/64

 

 

9.2

0.3622

 

 

Tapping Drill ISO Metric Special Pitches 10 mm

9.3

0.3661

 

U

Tapping Drill 7/16 Whitworth

9.4

0.3701

 

 

Tapping Drill 7/16 UNC

9.5

0.3740

 

V

Tapping Dnll ISO Metric Coarse 11 mm

9.53

0.3750

3/8

 

 

9.6

0.3780

 

 

 

9.7

0.3819

 

 

Tapping Drill 7/16 BSF

9.8

0.3858

 

W

 

9.9

0.3898

 

 

Tapping Drill 7/16 UNF

9.92

0.3906

25/64

 

 

10

0.3937

 

 

 

10.1

0.3976

 

X

Tapping Drill 7/16 BSC

10.2

0.4016

 

 

Tapping Drill ISO Metric Coarse 12 mm

10.3

0.4055

 

Y

 

10.32

0.4062

13/32

 

 

10.4

0.4094

 

 

 

10.5

0.4134

 

Z

Tapping Drill 1/2 Whitworth and  ISO Metric Special Pitches 12 mm (1.5 mm pitch)

10.6

0.4173

 

 

 

10.7

0.4213

 

 

 

10.72

0.4219

27/64

 

 

10.8

0.4252

 

 

Tapping Drill 1/2 UNC and ISO Metric Fine 12 mm

10.9

0.4291

 

 

 

11

0.4331

 

 

Tapping Drill ISO Metric Special Pitches 12 mm (1mm pitch)

11.1

0.4370

 

 

 

11.11

0.4375

7/16

 

Tapping Drill 1/2 BSF

11.2

0.4409

 

 

Tapping Drill 1/4 BSTP

11.3

0.4449

 

 

 

11.4

0.4488

 

 

Tapping Drill 1/2 UNF

11.5

0.4528

 

 

 

11.51

0.4531

29/64

 

 

11.6

0.4567

 

 

 

11.7

0.4606

 

 

 

11.8

0.4646

 

 

Tapping Drill 1/4 BSP

11.9

0.4685

 

 

 

11.91

0.4688

15/32

 

 

12

0.4724

 

 

Tapping Drill ISO Metric Coarse 14 mm

12.1

0.4764

 

 

Tapping Drill 9/16 Whitworth

12.2

0.4803

 

 

Tapping Drill 9/16 UNC

12.3

0.4843

 

 

 

12.3

0.4844

31/64

 

 

12.4

0.4882

 

 

 

12.5

0.4921

 

 

Tapping Drill ISO Metric Special Pitches 14 mm

12.6

0.4961

 

 

 

12.7

0.5000

1/2

 

Tapping Drill 9/16 BSF

12.8

0.5039

 

 

Tapping Drill ISO Metric Fine 14 mm

12.9

0.5079

 

 

Tapping Drill 9/I 6 UNF

13

0.5118

 

 

 

13.1

0.5156

33/64

 

Tapping Drill 9/16 BSC and 9/16 CEI

13.1

0.5157

 

 

 

13.2

0.5197

 

 

 

13.3

0.5236

 

 

 

13.4

0.5276

 

 

 

13.49

0.5313

17/32

 

Tapping Drill 5/8 UNC

13.5

0.5315

 

 

Tapping Drill 5/8 Whitworth

13.6

0.5354

 

 

 

13.7

0.5394

 

 

 

13.8

0.5433

 

 

 

13.89

0.5469

35/64

 

 

13.9

0.5472

 

 

 

14

0.5512

 

 

Tapping Drill ISO Metric Coarse 16 mm and 5/8 BSF

14.25

0.5610

 

 

 

14.3

0.5625

9/16

 

 

14.5

0.5709

 

 

Tapping Drill 5/8 UNF and ISO Metric Fine 16 mm

14.68

0.5780

37/64

 

 

14.75

0.5807

 

 

Tapping Drill 3/8 BSTP

15

0.5906

 

 

Tapping Drill 11/16 Whitworth, ISO Metric Special Pitches 16 mm and 5/8 BSC

15.08

0.5937

19/32

 

 

15.25

0.6004

 

 

Tapping Drill 3/8 BSP

15.48

0.6094

39/64

 

 

15.5

0.6102

 

 

Tapping Drill ISO Metric Coarse 18 mm and 11/16 BSF

15.75

0.6201

 

 

 

15.88

0.6252

5/8

 

 

16

0.6299

 

 

 

16.25

0.6398

 

 

 

16.27

0.6406

41/64

 

Tapping Drill 3/4 Whitworth

16.5

0.6496

 

 

Tapping Drill 3/4 UNC and ISO Metric Fine 18 mm

16.67

0.6563

21/32

 

 

16.75

0.6594

 

 

Tapping Drill 3/4 BSF

17

0.6693

 

 

 

17.07

0.6720

43/64

 

 

17.25

0.6791

 

 

 

17.46

0.6874

11/16

 

Tapping Drill 3/4 UNF

17.5

0.6890

 

 

Tapping Drill ISO Metric Coarse 20 mm

17.75

0.6988

 

 

 

17.86

0.7031

45/64

 

 

18

0.7087

 

 

Tapping Drill 13/16 Whitworth and ISO Metric Special Pitches 20 mm (2 mm pitch)

18.25

0.7185

 

 

Tapping Drill 1/2 BSTP

18.26

0.7189

23/32

 

 

18.5

0.7283

 

 

Tapping Drill ISO Metric Fine 20 mm

18.65

0.7343

47/64

 

 

18.75

0.7382

 

 

 

19

0.7480

 

 

Tapping Drill ISO Metric Special Pitches 20 mm (1 mm pitch)

19.05

0.7500

3/4

 

Tapping Drill 1/2 BSP

19.25

0.7579

 

 

Tapping Drill 7/8 Whitworth

19.45

0.7656

49/64

 

Tapping Drill 7/8 UNC

19.5

0.7677

 

 

Tapping Drill ISO Metric Coarse 22 mm

19.75

0.7776

 

 

 

19.84

0.7812

25/32

 

Tapping Drill 7/8 BSF

20

0.7874

 

 

 

20.24

0.7969

51/64

 

 

20.25

0.7972

 

 

 

20.5

0.8071

 

 

Tapping Drill ISO Metric Fine 22 mm

20.64

0.8125

13/16

 

Tapping Drill 7/8 UNF

20.75

0.8169

 

 

Tapping Drill 15/16 Whitworth

21

0.8268

 

 

Tapping Drill ISO Metric Coarse 24 mm

21.03

0.8281

53/64

 

Tapping Drill 5/8 BSP

21.25

0.8366

 

 

 

21.43

0.8438

27/32

 

 

21.5

0.8465

 

 

 

21.75

0.8563

 

 

 

21.83

0.8594

55/64

 

 

22

0.8661

 

 

Tapping Drill 1 inch Whitworth and ISO Metric Fine 24 mm

22.23

0.8750

7/8

 

 

22.25

0.8760

 

 

Tapping Drill I UNC

22.5

0.8858

 

 

Tapping Drill ISO Metric Special Pitches 24 mm (1.5 mm pitch)

22.62

0.8906

57/64

 

 

22.75

0.8957

 

 

Tapping Drill 1 inch BSF

23

0.9055

 

 

Tapping Drill ISO Metric Special Pitches 24 mm (1 mm pitch)

23.02

0.9062

29/32

 

 

23.25

0.9154

 

 

Tapping Drill I inch UNF

23.42

0.9219

59/64

 

 

23.5

0.9252

 

 

Tapping Drill ISO Metric Special Pitches 25 mm (1.5 mm pitch)

23.75

0.9350

 

 

Tapping Drill 3/4 BSTP

23.81

0.9375

15/16

 

 

24

0.9449

 

 

Tapping Drill ISO Metric Coarse 27 mm

24.21

0.9531

61/64

 

 

24.25

0.9547

 

 

 

24.5

0.9646

 

 

Tapping Drill 3/4 BSP

24.61

0.9688

31/32

 

Tapping Drill 1inch BSC and 1 inch CEI

24.75

0.9744

 

 

 

25

0.9843

 

 

Tapping Drill ISO Metric Fine 27 mm

25

0.9844

63/64

 

 

25.4

1.0000

1

 

 

 

 

 

 

Standards rise in Increments of 1/64in and 0.50 mm.

 
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