UNC and UNF TPI chart

Threads per inch for the UNC coarse and UNF fine series by bolt size.

UNC and UNF TPI chart
Bolt size no. or inches Threads per inch (TPI)
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