Fluid Mechanics
Orifice Flow Calculator
This calculator uses the basic orifice flow equation to determine volumetric flow rate from an orifice plate. The discharge coefficient (Cd) and fluid density must be supplied by the user. This is not an ISO 5167 compliant sizing tool — it uses the simplified incompressible liquid orifice relation.
TypeInteractive calculator — separate from unit conversions
Calculator
User-supplied — not calculated or recommended. Visible and editable.
User-supplied — no lookup
Result
Volumetric flow (Q)0.0217769 m³/s
Orifice area (A)0.00785398 m²
Velocity through orifice2.77272 m/s
Formulas
Orifice area
A = π × d² / 4
Volumetric flow
Q = Cd × A × √(2 × ΔP / ρ)
ΔP from flow (reverse)
ΔP = ½ρ × (Q / (Cd × A))²
Diagram
Worked example
Orifice diameter d = 0.1 m, Cd = 0.62, ΔP = 10,000 Pa, ρ = 1000 kg/m³. What is the volumetric flow rate?
- 01A = π × 0.1² / 4 = 0.00785398 m²
- 02Q = 0.62 × 0.00785398 × √(2 × 10,000 / 1000)
- 03Q = 0.004870 × √20
- 04Q = 0.004870 × 4.4721
- 05Q ≈ 0.02178 m³/s
Result
The volumetric flow rate is approximately 0.02178 m³/s.
FAQ
Is this ISO 5167 compliant orifice sizing?
No. This uses the simplified orifice flow equation. ISO 5167 compliant sizing requires beta-ratio corrections, upstream/downstream geometry, and other factors that are not implemented.
Does this calculate or recommend Cd?
No. The discharge coefficient must be supplied by the user. This calculator does not calculate Cd from geometry or standards.
Does this apply gas expansibility?
No. Gas expansibility factor (Y or ε) is not included. This calculator uses the incompressible liquid relation only.
Is this suitable for custody-transfer measurement?
No. Custody-transfer orifice measurement requires ISO 5167 or equivalent standard compliance, which this calculator does not provide.
Does this calculate permanent pressure loss?
No. Permanent pressure loss across the orifice plate is not calculated. Only the flow rate from the measured differential pressure is determined.