D ecimal
equivalents
Inch/Metric Tap Drill Sizes & Decimal Equivalents
Drill Size
19
39 32
64
41
64 21
43 32
64
45
64 23
47 32
64
49
64 25
51 32
64
53
64 27
55 32
64
57
64 29
59 32
64
61
64 31
63 32
64
13/64
17/64
111/64
17/32
5
8
11
16
3
4
13
16
7
8
15
16
1
11/8
11/4
119/64
111/32
13/8
127/64
11/2
Decimal
EQUIVALENT
.5938
.6094
.6250
.6406
.6562
.6719
.6875
.7031
.7188
.7344
.7500
.7656
.7812
.7969
.8125
.8281
.8438
.8594
.8750
.8906
.9062
.9219
.9375
.9531
.9688
.9844
1.0000
1.0469
1.1094
1.1250
1.1719
1.2188
1.2500
1.2969
1.3438
1.3750
1.4219
1.5000
Tap Size
3/4
- 10
3/4
- 16
7/8
7/8
-9
- 14
1-8
1 - 12
1 - 14
11/8 - 7
11/8 - 12
11/4 - 7
11/4 - 12
13/8 - 6
13/8 - 12
11/2 - 6
11/2 - 12
pipe thread Sizes (npsc)
thread
drill
thread
drill
1/8 – 27
11/32 11/2 – 111/2
13/4
1/4 – 18
7/16
1
2 – 11 /2 27/32
3/8 – 18
37/64 21/2 – 8
221/32
1/2 – 14
23/32
3–8
31/4
3/4 – 14
59/64 31/2 – 8
33/4
1 – 111/2 15/32
4–8
41/4
11/4 – 111/2 11/2
Bulletin 1317-150M/T 10/11
Metric Tap
Metric Tap Drill Sizes
Tap Drill (mm)
Decimal (Inch)
M1.6 x 0.35
M1.8 x 0.35
M2 x 0.4
M2.2 x 0.45
M2.5 x 0.45
M3 x 0.5
M3.5 x 0.6
M4 x 0.7
M4.5 x 0.75
M5 x 0.8
M6 x 1
M7 x 1
M8 x 1.25
M8 x 1
M10 x 1.5
M10 x 1.25
M12 x 1.75
M12 x 1.25
M14 x 2
M14 x 1.5
M16 x 2
M16 x 1.5
M18 x 2.5
M18 x 1.5
M20 x 2.5
M20 x 1.5
M22 x 2.5
M22 x 1.5
M24 x 3
M24 x 2
M27 x 3
M27 x 2
M30 x 3.5
M30 x 2
M33 x 3.5
M33 x 2
M36 x 4
M36 x 3
M39 x 4
M39 x 3
1.25
1.45
1.60
1.75
2.05
2.50
2.90
3.30
3.70
4.20
5.00
6.00
6.70
7.00
8.50
8.70
10.20
10.80
12.00
12.50
14.00
14.50
15.50
16.50
17.50
18.50
19.50
20.50
21.00
22.00
24.00
25.00
26.50
28.00
29.50
31.00
32.00
33.00
35.00
36.00
.0492
.0571
.0630
.0689
.0807
.0984
.1142
.1299
.1457
.1654
.1968
.2362
.2638
.2756
.3346
.3425
.4016
.4252
.4724
.4921
.5512
.5709
.6102
.6496
.6890
.7283
.7677
.8071
.8268
.8661
.9449
.9843
1.0433
1.1024
1.1614
1.2205
1.2598
1.2992
1.3780
1.4173
starrett.com
D ecimal
equivalents
Inch/Metric Tap Drill Sizes & Decimal Equivalents
Drill Size
decimal
EQUIV.
tap size
80 .0135
79 .0145
1
.0156
64
78 .0160
77 .0180
76 .0200
75 .0210
74 .0225
73 .0240
72 .0250
71 .0260
70 .0280
69 .0292
1 68 .0310
.0312
32
67 .0320
66 .0330
65 .0350
64 .0360
63 .0370
62 .0380
61 .0390
60 .0400
59 .0410
58 .0420
57 .0430
56 .0465
3
.0469 0 - 80
64
55 .0520
54 .0550
1 53 .0595 1 - 64, 72
.0625
16
52 .0635
51 .0670
50 .0700 2 - 56, 64
49 .0730
48 .0760
5
.0781
64
47 .0785 3 - 48
46 .0810
45 .0820 3 - 56
44 .0860
43 .0890 4 - 40
3 42 .0935 4 - 48
.0938
32
41 .0960
40 .0980
39 .0995
38 .1015 5 - 40
Drill Size
decimal
EQUIV.
37 .1040
36 .1065
7
.1094
64
35 .1100
34 .1110
33 .1130
32 .1160
1 31 .1200
8 30 .1250
.1285
29 .1360
28 .1405
9
.1406
64
27 .1440
26 .1470
25 .1495
24 .1520
5 23 .1540
32 22 .1562
.1570
21 .1590
20 .1610
19 .1660
18 .1695
11
.1719
64
17 .1730
16 .1770
15 .1800
14 .1820
3 13 .1850
16 12 .1875
.1890
11 .1910
10 .1935
9 .1960
8 .1990
7 .2010
13
.2031
64
6 .2040
5 .2055
4 .2090
7 3 .2130
32 2 .2188
.2210
1 .2280
.2340
A
15
.2344
64
B .2380
C .2420
tap size
5 - 44
6 - 32
6 - 40
8 - 32, 36
10 - 24
10 - 32
12 - 24
12 - 28
1/4 -
20
1/4 -
28
Drill Size
decimal
EQUIV.
.2460
1 D
4 E .2500
F .2570
G .2610
17
.2656
64
H .2660
I .2720
J .2770
9 K .2810
.2812
32
L .2900
M
.2950
19
.2969
64
N
.3020
5
.3125
16
O .3160
P
.3230
21
.3281
64
Q .3320
11 R .3390
.3438
32
S .3480
T
.3580
23
.3594
64
3 U .3680
.3750
8
V .3770
W .3860
25
.3906
64
X .3970
Y
.4040
13
.4062
32
Z .4130
27
.4219
64 7
.4375
29 16
.4531
64
15
.4688
32
31
.4844
64 1
.5000
33 2
.5156
64
17
.5312
32
35
.5469
64 9
.5625
37 16
.5781
64
tap size
5/16 -
18
5/16 -
24
3/8 -
16
3/8 -
24
7/16 -
14
7/16 -
20
1/2 -
13
1/2 -
20
9/16 -
12
9/16 -
18
5/8 -
11
5/8 -
18
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