Volumetric Flow Calculator Formula

Understand the math behind the volumetric flow calculator. Each variable explained with a worked example.

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Formulas Used

Volume Flow Rate

flow_m3s = velocity * area

Volume Flow Rate

flow_lpm = velocity * area * 60000

Volume Flow Rate

flow_gpm = velocity * area * 15850.3

Volume Flow Rate

flow_m3h = velocity * area * 3600

Variables

VariableDescriptionDefault
velocityFluid Velocity (V)(m/s)3
diameterPipe Inner Diameter (D)(mm)150
d_mDerived value= diameter / 1000calculated
areaDerived value= pi * pow(d_m, 2) / 4calculated

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.

velocity = 3diameter = 150
  1. 01D = 150 mm = 0.15 m
  2. 02A = pi × 0.15² / 4 = 0.01767 m²
  3. 03Q = 3 × 0.01767 = 0.05301 m³/s
  4. 04Q = 0.05301 × 60000 = 3180.9 L/min
  5. 05Q = 0.05301 × 15850.3 = 840.2 GPM

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