Calculate the required orifice area or the actual flow through a restrictor from pressure drop, density and discharge coefficient.
Set the inputs and run the calculation.
Calculate required opening area from flow, pressure drop and discharge coefficient.
Flow Q, pressure drop Δp, density ρ, discharge coefficient Cᵈ and optional existing diameter.
The discharge coefficient captures geometry, edge shape and flow loss. For the same flow, an unfavorable, sharp-edged or dirty opening needs more area and causes more pressure drop.
For incompressible flow Q = Cᵈ·A·√(2Δp/ρ), giving area and equivalent diameter.
A lower Cᵈ for a sharp-edged geometry requires a larger opening for the same flow.
Sources and limits: Orifice equation; ISO 5167 applies only to its defined measurement plates and installation, not every valve.
Calculate required opening area from flow, pressure drop and discharge coefficient.
Hydraulic calculations link pressure difference, effective area and flow. Pressure determines force, flow determines speed, while line losses and efficiency reduce ideal values.
For incompressible flow Q = Cᵈ·A·√(2Δp/ρ), giving area and equivalent diameter.
Flow Q, pressure drop Δp, density ρ, discharge coefficient Cᵈ and optional existing diameter. The discharge coefficient captures geometry, edge shape and flow loss. For the same flow, an unfavorable, sharp-edged or dirty opening needs more area and causes more pressure drop.
Enter flow, target pressure drop, fluid density and the discharge coefficient Cᵈ of the planned opening shape. The calculator returns the required opening area and equivalent diameter.
A lower Cᵈ for a sharp-edged geometry requires a larger opening for the same flow.
The discharge coefficient captures geometry, edge shape and flow loss. For the same flow, an unfavorable, sharp-edged or dirty opening needs more area and causes more pressure drop. The result is a pre-sizing point. Higher pressure raises cylinder force; more flow raises speed but usually also increases losses and heat.
Flow in l/min, pressure drop in bar, density in kg/m³, area in mm², diameter in millimetres.
Sizing a restrictor or orifice for a target pressure drop at known flow, or estimating flow through an existing opening of known size.
Orifice equation; ISO 5167 applies only to its defined measurement plates and installation, not every valve.
Common mistake: Don't set discharge coefficient Cᵈ to 1 by default – sharp-edged or fouled openings have noticeably lower values, requiring a larger area for the same flow. This equation applies to incompressible liquids; compressible gases at a large pressure ratio need a different approach.
Edge shape (sharp versus rounded), the ratio of opening to line diameter, and the flow's Reynolds number; supplier data or measurements are more accurate than generic table values.
Flow enters pressure drop squared (Δp ∝ Q²/A²); a smaller area at the same flow therefore raises pressure drop disproportionately.
Only approximately for one fixed opening state; real valves often have a nonlinear Cᵈ over stroke that should come from the manufacturer's curve.
Pre-size a restrictor for a target liquid flow and pressure drop.
Results are preliminary engineering estimates. Component approval, safety functions, material, fatigue, installation checks and the complete system assessment remain separate.