| Author, Origin & Date | Formula |
| Hydraulic Institute (1998) [1] | D・(1 + 2.3・Fr) |
| Pumping System Manual | (V2/2g) + 0.5 |
| Prosser (1977) [2] | 1.5 * D |
| Paterson & Noble (1982) | D・(1.5 + 2.5・Fr) |
| Hecker (1987) [3] | D・(1 + 2.3Fr) |
| Knauss (1987) [4] | D・(0.5 + 2・Fr) |
| Flyght (2002) [5] | 1.7・Fr |
| Werth & Frizzell (2009) [6] | D・(2.1 + 1.33・Fr0.67) |