text: This similarity between the Chézy and Manning formulas shown above also means that the standardized Manning coefficients may be used to estimate open channel flow velocity with the Chézy formula, by using them to calculate the Chézy's coefficient as shown below. Manning derived the following relationship between Manning coefficient () to Chézy coefficient () based upon experiments:
  where
  *  is the Chézy coefficient [length/time], a function of relative roughness and Reynolds number;
  *  is the hydraulic radius, which is the cross-sectional area of flow divided by the wetted perimeter (for a wide channel this is approximately equal to the water depth) [m];
  *  is Manning's coefficient [time/length]; and
  *  is a constant; k = 1 when using SI units and k = 1.49 when using BG units.