Drainage Grate Flow Calculators
Calculate the flow of water through a drainage grate. Weir and Orifice calculators are used to determine the inlet capacity in sag (ponding) condition to help choose the proper grate for your project. Below outlines the EJ equations used in our calculations. Q = Flow (CFS, cubic feet per second) A = Open area in grate (inches2) d = Depth of water over grate (inches) Coefficient = 0.0108 Q = Flow (CFS, cubic feet per second) L = Perimeter of grate where flow is present (in feet) H = Depth of water (in feet) Coefficient = 3.33 Q = Flow (CFS, cubic feet per second) A = Open area in grate (inches2) d = Depth of water over grate (inches) Coefficient = 0.0108 Q = Flow (CFS, cubic feet per second) L = Perimeter of grate where flow is present (in feet) H = Depth of water (in feet) Coefficient = 3.33
Weir Flow Calculator
Select Grate Type
Not sure?
Curb Inlets include rectangular or square grates situated against a curb.
Orifice Flow Calculator
About Our Calculations
Q = 0.0108A√d
Q = 3.33L(H) 3/2
Orifice Equation
Q = 0.0108A√d
Weir Equation
Q = 3.33L(H) 3/2
Q = Flow capacity (in cubic feet per second)
C = Orifice coefficient
A = Open area of grate (ft2 )
g = Acceleration due to gravity (32.2ft/sec2 )
d = Depth of water over grate (in feet)
Using an Orifice coefficient of 0.67 and correcting open area from square feet to square inches and depth of water from feet to inches, this equation simplifies to: THE ORIFICE EQUATION.
