The size of the brake pipe is measured in inches. The United States uses NPT (National Pipe Thread Tapered) threads, which are 1/8 inch per foot. For example, if the brake pipe measures 4 feet long, then it has 4 x 1/8 = 0.4 NPT thread taper on it.
The most popular size of brake pipe in use is 3/16 inch.
The following list shows the most common sizes, but other sizes can be found.
| Size | Explaination |
|---|---|
| 1/8″ NPT | This size is a less common size in the United States, but it does see use on some lighter weight trailers and specialty light truck equipment. |
| 1/4″ NPT | This size of brake pipe is very common for heavy duty trucking. |
| 5/32″ NPT | This size is a less common size in the United States, but it does see use on some lighter weight trailers and specialty light truck equipment. |
| 1/4″ NPT | This size of brake pipe is very common for heavy duty trucking. |
| 3/8″ NPT | This size of brake pipe is used on heavier equipment, such as dump trucks and semi-tractors. |
| 1/2″ NPT | This size of brake pipe is most commonly found on construction equipment, such as excavators. |
| 5/8″ NPT | This size of brake pipe is most commonly found on large construction equipment, such as cranes and bulldozers. |
| 3/4″ NPT | This size of brake pipe is used on extremely heavy-duty equipment, such as large tractors. |
| 1″ NPT | This size of brake pipe is uncommon in the United States but it commonly seen in other countries. |
