The Flow Rate Pressure Calculator helps determine the relationship between fluid flow rate and pressure difference across a section of pipe or an orifice. It is widely used in fields like fluid mechanics, HVAC system design, irrigation, water supply networks, and industrial engineering. With this calculator, you can estimate how much fluid moves through a system based on pressure, pipe size, and fluid properties — or reverse the process to estimate the pressure needed for a certain flow.
This calculator falls under the fluid dynamics and hydraulic systems calculator category.
formula of Flow Rate Pressure Calculator
- Flow Rate from Pressure Drop in Pipes (Metric System)
Q = C × A × √(2 × ΔP / ρ)
Where:
Q = Flow rate (m³/s or L/s)
C = Discharge coefficient (typically between 0.6 and 0.9)
A = Cross-sectional area of pipe/orifice (in m²)
ΔP = Pressure drop (Pa or N/m²)
ρ = Density of the fluid (kg/m³)
- Volumetric Flow Rate (Imperial Units)
Q = Cv × √(ΔP / SG)
Where:
Q = Flow rate in gallons per minute (GPM)
Cv = Flow coefficient (dimensionless, specific to device)
ΔP = Pressure drop (psi)
SG = Specific gravity of the fluid (for water = 1)
- Solving for Pressure Drop (Rearranged)
ΔP = (Q / (C × A))² × (ρ / 2)
This version is useful when you know the flow rate and want to estimate how much pressure is needed to achieve it.
Common Conversion and Reference Table
| Fluid Type | Density (kg/m³) | Typical Cv (valve) | Specific Gravity |
|---|---|---|---|
| Water (20°C) | 998 | 12–200 | 1.0 |
| Air (at STP) | 1.225 | 20–100 | 0.0012 |
| Diesel Fuel | 850 | 15–180 | 0.85 |
| Seawater | 1025 | 12–180 | 1.025 |
This table helps users estimate flow or pressure without always recalculating base data.
Example of Flow Rate Pressure Calculator
Let’s say you want to calculate the flow rate through a pipe where:
- Pressure drop ΔP = 50000 Pa
- Area A = 0.005 m²
- Density ρ = 1000 kg/m³ (water)
- Discharge coefficient C = 0.8
Use the formula:
Q = 0.8 × 0.005 × √(2 × 50000 / 1000)
Q = 0.8 × 0.005 × 10 = 0.04 m³/s
So, the flow rate is 0.04 cubic meters per second or 40 liters per second.
Most Common FAQs
If you don’t have the exact value, use a common estimate of 0.7 to 0.8 for many pipe or nozzle setups. For precise systems, always refer to manufacturer data.
Yes, but the density and specific gravity need to be adjusted accordingly. Since gas compressibility is a factor, ensure constant pressure and temperature conditions for accuracy.
Yes, but indirectly. You can calculate the pressure needed to push a certain flow through a system, which helps in selecting a pump with matching specs.