The following formulæ have been adapted for water flowing in circular pipes, using the following units: volume flow rate ($Q$) in L/s; head loss ($h_L$) and pipelength ($L$) in m; pipe diameter ($D$) in mm. The resistance coefficient $C$ has no units.

\[ Q = \frac{CD^{2.63}\left(\frac{h_L}{L}\right)^{0.54}}{279000} \]

\[ D = \left(\frac{279000Q}{C\left(\frac{h_L}{L}\right)^{0.54}}\right)^{0.3802} \]

\[ h_L = L\left(\frac{279000Q}{CD^{2.63}}\right)^{1.852} \]