BSP 

Nominal Size [Inch]    D1 mm (")        D2 mm (")        P mm (")     
1/2 20.96 (0.83) 18.63 (0.73) 1.81 (0.07)
3/4 26.41 (1.04) 24.12 (0.95) 1.81 (0.07)
1 33.25 (1.31) 30.29 (1.19) 2.31 (0.09)
1 1/4 41.6 (1.64) 39.3 (1.55) 2.31 (0.09)
1 1/2 47.80 (1.88) 44.85 (1.77) 2.31 (0.09)
2 59.61 (2.35) 56.66 (2.23) 2.31 (0.09)
3 87.88 (3.46) 84.93 (3.34) 2.31 (0.09)
4 113.03 (4.45) 110.07 (4.33) 2.31 (0.09)


NPT
Nominal Size [Inch]    D1 mm (")        D2 mm (")        P mm (")     
1/2 21.22 (0.84) 18.32 (0.72) 1.81 (0.07)
3/4 26.57 (1.05) 23.77 (0.93) 1.81 (0.07)
1 33.23 (1.31) 29.69 (1.17) 2.21 (0.09)
1 1/2 48.05 (1.89) 44.52 (1.75) 2.21 (0.09)
2 60.09 (2.37) 56.56 (2.23) 2.21 (0.09)
3 88.61 (3.49) 83.53 (3.29) 3.18 (0.13)
4 113.97 (4.49) 108.89 (4.29) 3.18 (0.13)

[Parallel threads can be measured at any length, tapered threads must be measured at the gauge length.]