What is Tooth Per Inch (TPI)?

The coarseness of saw blades is measured as the number of TPI. This is measured between the bottoms, or gullets, of the teeth.

Pitch is the axial distance between adjacent repeating features on a mechanical element. TPI is an imperial unit of measurement for pitch, commonly used in the United States.
As its name suggests, it is the number of times in which the feature appears over a linear distance of 1″ (25.4 mm)

Examples for mechanical elements with a pitch:

  • Screws / Threads
  • Knurls
  • Saw blades
  • Milling Cutters

				

					

						

						

						

					

					

				

			

			

				
TPI Conversion Formulas

				

					
  

					

						
TPI=1/P(P in Inches)

						
TPI=(25.4)/P (P in mm)

						
P=1/TPI (P in Inches) 

						
P=(25.4)/TPI (P in mm)

					

				

			

			

				
TPI Conversion Chart

				

					

						Threads per inch
						Pitch in inches
						Pitch in mm
					

					

						127
						0.00787
						0.200
					

					

						120
						0.00833
						0.212
					

					

						112
						0.00893
						0.227
					

					

						101.6
						0.00984
						0.250
					

					

						100
						0.01000
						0.254
					

					

						96
						0.01042
						0.265
					

					

						90
						0.01111
						0.282
					

					

						84.67
						0.01181
						0.300
					

					

						72.57
						0.01378
						0.350
					

					

						72
						0.01389
						0.353
					

					

						64
						0.01563
						0.397
					

					

						63.5
						0.01575
						0.400
					

					

						60
						0.01667
						0.423
					

					

						56.44
						0.01772
						0.450
					

					

						56
						0.01786
						0.454
					

					

						50.8
						0.01969
						0.500
					

					

						48
						0.02083
						0.529
					

					

						44
						0.02273
						0.577
					

					

						42.33
						0.02362
						0.600
					

					

						40
						0.02500
						0.635
					

					

						36.29
						0.02756
						0.700
					

					

						36
						0.02778
						0.706
					

					

						34
						0.02941
						0.747
					

					

						33.87
						0.02952
						0.750
					

					

						32
						0.03125
						0.794
					

					

						31.75
						0.03150
						0.800
					

					

						30
						0.03333
						0.847
					

					

						28.22
						0.03544
						0.900
					

					

						28
						0.03571
						0.907
					

					

						27
						0.03704
						0.941
					

					

						26
						0.03846
						0.977
					

					

						25.4
						0.03937
						1.000
					

					

						24
						0.04167
						1.058
					

					

						22
						0.04545
						1.155
					

					

						20.32
						0.04921
						1.250
					

					

						20
						0.05000
						1.270
					

					

						19
						0.05263
						1.337
					

					

						18
						0.05556
						1.411
					

					

						16.93
						0.05907
						1.500
					

					

						16
						0.06250
						1.588
					

					

						14.51
						0.06892
						1.751
					

					

						14
						0.07143
						1.814
					

					

						13
						0.07692
						1.954
					

					

						12.7
						0.07874
						2.000
					

					

						12
						0.08333
						2.117
					

					

						11.50
						0.08696
						2.209
					

					

						11
						0.09091
						2.309
					

					

						10.16
						0.09843
						2.500
					

					

						10
						0.10000
						2.540
					

					

						9
						0.11111
						2.822
					

					

						8.47
						0.11806
						2.999
					

					

						8
						0.12500
						3.175
					

					

						7.26
						0.13774
						3.499
					

					

						7
						0.14286
						3.629
					

					

						6.35
						0.15748
						4.000
					

					

						6
						0.16667
						4.233
					

					

						5.64
						0.17730
						4.504
					

					

						5.08
						0.19685
						5.000
					

					

						5
						0.20000
						5.080
					

					

						4.62
						0.21645
						5.498
					

					

						4.5
						0.22222
						5.644
					

					

						4.23
						0.23641
						6.005
					

					

						4
						0.25000
						6.350
					

					

						3
						0.33333
						8.467
					

					

						2
						0.50000
						12.700