Calculate orifice flow rate, area, or velocity from any two known values with unit conversions and step-by-step results for m³/s, m², and m/s.
Orifice Velocity Formula
The calculator uses the continuity relationship between flow rate, orifice area, and velocity. If you enter any two values, the missing value is calculated from the same base equation.
Q = A * v
- Q = orifice flow rate
- A = orifice area
- v = orifice velocity
To calculate orifice velocity:
v = Q / A
To calculate orifice area:
A = Q / v
To calculate orifice flow rate:
Q = A * v
The calculator first converts your inputs to base SI units: cubic meters per second for flow rate, square meters for area, and meters per second for velocity. It then applies the matching formula and converts the result back to the unit you selected.
Common Unit Conversions for Orifice Flow Calculations
These are the conversion factors used to keep the units consistent during the calculation.
| Quantity | Unit | Equivalent SI Value |
|---|---|---|
| Flow rate | 1 ft³/s | 0.0283168 m³/s |
| Flow rate | 1 L/s | 0.001 m³/s |
| Flow rate | 1 gal/s | 0.00378541 m³/s |
| Area | 1 ft² | 0.092903 m² |
| Area | 1 cm² | 0.0001 m² |
| Area | 1 in² | 0.00064516 m² |
| Velocity | 1 ft/s | 0.3048 m/s |
Velocity Results and Basic Interpretation
| Result | What It Means |
|---|---|
| Higher velocity | The same flow is passing through a smaller area, or a larger flow is passing through the same area. |
| Lower velocity | The flow is spread across a larger area, or the flow rate is smaller. |
| Zero area | Velocity cannot be calculated because division by zero is not valid. |
| Very small area | The calculated velocity can become very large, so check that the area unit is entered correctly. |
Example Calculations
Example 1: Calculate orifice velocity
You have a flow rate of 0.20 m³/s and an orifice area of 0.05 m².
v = Q / A
v = 0.20 / 0.05 = 4 m/s
The orifice velocity is 4 m/s.
Example 2: Calculate flow rate
You have an orifice area of 12 in² and a velocity of 8 ft/s.
Convert area to square feet:
12 in^2 / 144 = 0.08333 ft^2
Apply the flow rate formula:
Q = A * v = 0.08333 * 8 = 0.6667 ft^3/s
The flow rate is 0.6667 ft³/s.
FAQ
What is orifice velocity?
Orifice velocity is the speed of fluid as it passes through an orifice opening. It is calculated by dividing the volumetric flow rate by the cross-sectional area of the orifice.
Is this the same as discharge through an orifice?
This calculator uses the simple continuity equation, Q = A × v. It does not include a discharge coefficient, pressure drop, fluid density, or losses. For real discharge through a sharp-edged orifice, those factors may be needed.
Why do the units matter so much?
Flow rate, area, and velocity must be in compatible units. For example, if flow rate is in m³/s and area is in m², velocity will be in m/s. If mixed units are entered, the values must be converted before the formula is applied.
