Flow Rate Calculator

Volumetric flow rate (Q) measures the volume of fluid passing a given point per unit of time. It is expressed in units such as m³/s, L/min, or gallons per minute (GPM). It differs from mass flow rate, which accounts for the fluid's density.

Use the formula Q = V / t, where V is the volume of fluid and t is the time taken for that volume to pass. For example, 500 litres flowing in 60 seconds gives Q = 500/60 ≈ 8.33 L/s.

First calculate the pipe's cross-sectional area: A = π × (d/2)². Then multiply by the average fluid velocity: Q = A × v. For example, a 50 mm diameter pipe with fluid moving at 2 m/s gives Q ≈ 0.003927 m³/s.

Multiply volumetric flow rate by the fluid's density: ṁ = Q × ρ. For water at 1000 kg/m³, a flow rate of 0.001 m³/s gives a mass flow rate of 1 kg/s.

Maximum flow rate is the highest volume of fluid a pipe, pump, or system can move per unit time without exceeding design pressure or velocity limits. Exceeding it can cause turbulence, pressure loss, or pipe damage.

Rearrange the pipe-flow formula: v = Q / A, where A is the pipe's cross-sectional area (π × r²). This is useful when you know the flow rate and pipe size but need to verify the fluid velocity stays within safe limits.

Common metric units include m³/s, m³/h, and L/min. Imperial units include gallons per minute (GPM) and cubic feet per minute (CFM). Industrial applications often use m³/h or GPM, while scientific contexts favour m³/s.

Flow rate applies to garden hoses, shower heads, water supply pipes, fuel systems, HVAC ducts, and medical devices like IV drips or blood flow measurements. Understanding flow rate helps size pumps correctly and ensure adequate supply.