UNC UNF Threads Per Inch TPI Threads Per Inch

Thread Count (TPI) Explained - TPI stands for Threads Per Inch which is simply a count of the number of threads per inch measured along the length of a fastener. This description is used only with American fasteners. Metric Fasteners use a thread Pitch to designate different thread sizes.

Bolt Size No. or Inches	Threads Per Inch (TPI)
Bolt Size No. or Inches	Coarse Thread UNC	Fine Thread UNF
#0	-	80
#1	64	72
#2	56	64
#3	48	56
#4	40	48
#5	40	44
#6	32	40
#8	32	36
#10	24	32
#12	24	28
1/4	20	28
5/16	18	24
3/8	16	24
7/16	14	20
1/2	13	20
9/16	12	18
5/8	11	18
3/4	10	16
7/8	9	14
1	8	12
1-1/8	7	12
1-1/4	7	12
1-3/8	6	12
1-1/2	6	12
1-3/4	5
2	4-1/2
2-1/4	4-1/2
2-1/2	4
2-3/4	4
3	4
3-1/4	4
3-1/2	4
3-3/4	4
4	4

Releated References:
Screw Thread Limits Table
UNC UNF Threads Per Inch TPI Threads Per Inch
Wood Screw Pilot Hole Sizes Table
Standard NPT National Pipe Thread Tap Drill Sizes Table
ASTM ISO Metric Thread Sizes and Tap Drill Table
Metric Thread Size Tap Drill Table
Standard Tap Drills Clearance Holes Table
Standard Drill Sizes Decimal Equivalents Table
Socket Head Cap Screw Sizes Dimension Table
SAE Grade ASTM Bolt Identify Marks Mechanical Properties
Steel Bolt Torque Specifications Table
Finished Hex Nut Dimensions
Heavy Hex Nut Dimensions Table
Standard ANSI Type B Flat Washer Sizes