The specifications of steel pipes are calculated in millimeters of inner diameter.

Conversion between metric and English units

The conversion between metric and English units of steel pipes is as follows: the specification of English units is equal to 0.25 times of pipes with internal diameter 16 mm; The specification of English units is equal to 0.3 times that of pipes with an inner diameter of 20 mm; The specification of English units is equal to 0.04 times that of pipes with an inner diameter greater than 25mm.

Specification corresponding inner diameter

1 in 4 refers to the inner diameter of 8 mm in metric system and 2 mm in English system; 1 half refers to the metric 15 mm inner diameter, with 4 points in English; 3/4 refers to the inner diameter of 20 mm in metric system and 6 points in English system; 1 and 1 refer to the inner diameter of 32mm in metric system and 0.2 inch in imperial system.