Thread Pitch Conversion

APPROXIMATE PITCH/TPI – METRIC TO INCH CONVERSION CHART

Pitch (mm)	Calculated Pitch (inches)	Threads per inch	Pitch (inches)	Calculated Inch Pitch (mm)
0.20	0.007874	80	0.012500	0.32
0.25	0.009843	72	0.013899	0.35
0.30	0.011811	64	0.015625	0.40
0.35	0.013780	56	0.017857	0.45
0.40	0.015748	48	0.020833	0.53
0.45	0.017717	44	0.022727	0.58
0.50	0.019685	40	0.025000	0.64
0.55	0.021654	36	0.027778	0.71
0.60	0.023622	32	0.031250	0.79
0.65	0.025591	28	0.035714	0.91
0.70	0.027559	27	0.037037	0.94
0.75	0.029528	24	0.041667	1.06
0.80	0.031496	20	0.050000	1.27
1.00	0.039370	18	0.055556	1.41
1.25	0.049213	16	0.062500	1.59
1.50	0.059055	14	0.071429	1.81
1.75	0.068898	13	0.076923	1.95
2.00	0.078740	12	0.083333	2.12
2.50	0.098425	11.5	0.086957	2.21
3.00	0.118110	11	0.090909	2.31
3.50	0.137795	10	0.100000	2.54
4.00	0.157480	9	0.111111	2.82
4.50	0.177165	8	0.125000	3.18
5.00	0.196850	7	0.142857	3.63
5.50	0.216535	6	0.166667	4.23
6.00	0.236220	5	0.200000	5.08
8.00	0.314960	4.5	0.222222	5.64
		4	0.250000	6.35

Notes:

Column 1 is the Metric Pitch in “mm”

Column 2 is the approximate conversion of Column 1 to inches

Column 3 is the Base “Inch” Threads per Inch

Column 4 is the Calculated Pitch for the TPI in Column 3

Column 5 is the approximate conversion of the Inch TPI to “mm” Pitch

Columns 2 and 3 are not connected