Standard NPT Drill & Tap Sizes

NPT
Size

Tap Drill
Size (Inch)

Tap Drill Decimal
Equivalent (Inch)

1/16 - 27

C

0.242"

1/8 - 27

Q

0.332"

1/4 - 18

7/16"

0.438"

3/8 - 18

9/16"

0.562"

1/2 - 14

45/64"

0.703"

3/4 - 14

29/32"

0.906"

1.0 -11-1/2

1-9/64"

1.141"

1-1/4 - 11-1/2

1-31/64"

1.484"

1-1/2 - 11-1/2

1-23/32"

1-719"

2.0 - 11-1/2

2-3/16"

2.188"

2-1/2 - 8

2-39/64"

2.609

3.0 - 8

3-15/64"

3.234"

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