The easiest way, if you are replacing an existing item is to look at the body of the part to see if the size is stated.
To measure, you need the measure the widest thread on the male thread, see table below.
|
Metric Name |
BSP Name |
Diameter in mm |
Diameter in inches |
|
6mm |
1/8” |
9.728mm |
0.383 |
|
8mm |
¼” |
13.157mm |
0.518 |
|
10mm |
3/8” |
16.662mm |
0.656 |
|
15mm |
½” |
20.995mm |
0.825 |
|
20mm |
¾” |
26.441mm |
1.041 |
|
25mm |
1” |
33.249mm |
1.309 |
|
32mm |
1 ¼” |
41.91mm |
1.65 |
|
40mm |
1 ½” |
47.803mm |
1.882 |
|
50mm |
2” |
59.614mm |
2.347 |
|
65mm |
2 ½” |
75.184mm |
2.96 |
|
75mm or 80mm |
3” |
87.884mm |
3.46 |
|
100mm |
4” |
113.03mm |
4.45 |
|
125mm |
5” |
138.43mm |
5.45 |
|
150mm |
6” |
163.83mm |
6.45 |