Volumetric Flow Calculator Formula
Understand the math behind the volumetric flow calculator. Each variable explained with a worked example.
Formulas Used
Volume Flow Rate
flow_m3s = velocity * areaVolume Flow Rate
flow_lpm = velocity * area * 60000Volume Flow Rate
flow_gpm = velocity * area * 15850.3Volume Flow Rate
flow_m3h = velocity * area * 3600Variables
| Variable | Description | Default |
|---|---|---|
velocity | Fluid Velocity (V)(m/s) | 3 |
diameter | Pipe Inner Diameter (D)(mm) | 150 |
d_m | Derived value= diameter / 1000 | calculated |
area | Derived value= pi * pow(d_m, 2) / 4 | calculated |
How It Works
Volumetric Flow Rate
Volumetric flow rate is the volume of fluid passing through a cross-section per unit time. It is widely used in piping design, pump selection, and flow measurement.
Formula
Q = V × A = V × pi × D² / 4
where V is the average fluid velocity and A is the pipe cross-sectional area. Different industries use different units: m³/h in process, L/min in hydraulics, GPM in plumbing.
Worked Example
Water flowing at 3 m/s through a 150 mm pipe.
- 01D = 150 mm = 0.15 m
- 02A = pi × 0.15² / 4 = 0.01767 m²
- 03Q = 3 × 0.01767 = 0.05301 m³/s
- 04Q = 0.05301 × 60000 = 3180.9 L/min
- 05Q = 0.05301 × 15850.3 = 840.2 GPM
Frequently Asked Questions
How do I convert between GPM and m³/h?
1 GPM = 0.2271 m³/h, or 1 m³/h = 4.403 GPM. Multiply GPM by 0.2271 to get m³/h, or multiply m³/h by 4.403 to get GPM.
Does volumetric flow change with temperature?
For liquids, the change is usually small (water expands about 4% from 20°C to 80°C). For gases, volumetric flow changes significantly with temperature and pressure. This is why gas flows are often stated at standard conditions (STP or NTP).
What is normal vs actual volumetric flow for gases?
Normal flow (Nm³/h) is referenced to standard conditions (0°C, 1 atm). Actual flow is at operating conditions. Convert using the ideal gas law: Q_actual = Q_normal × (T_actual/T_normal) × (P_normal/P_actual).
Ready to run the numbers?
Open Volumetric Flow Calculator