Flow Rate Calculator
Calculate volumetric and mass flow rate for pipes and channels using the flow rate formula Q = A × v. Free online flow rate calculator with shape selection and instant results.
About This Calculator
The Flow Rate Calculator helps you compute the volumetric and mass flow rate of fluids through pipes and open channels. It is essential for engineers, plumbers, hydrologists, HVAC technicians, and physics students who need to determine how much fluid passes through a given cross-section per unit time.
The volumetric flow rate is calculated using the formula Q = A × v, where A is the cross-sectional area (computed from your shape selection) and v is the flow velocity. For circular pipes, the area is A = π × d² / 4. For rectangular channels, A = width × height. For triangular channels, A = ½ × width × depth. The mass flow rate is ṁ = ρ × Q, where ρ is the fluid density — enter 1000 kg/m³ for water, 1.225 kg/m³ for air, or look up your fluid's density.
Regional Notes
India: Flow rates in plumbing and irrigation are commonly expressed in liters per second (L/s) or cubic meters per hour (m³/h). Municipal water supply typically operates at 1–2 m/s velocity in pipes.
United States: Flow rates are often measured in gallons per minute (GPM) or cubic feet per second (cfs). 1 m³/s = 15,850.32 GPM. Common household faucet flow is 1–2.2 GPM.
United Kingdom: Flow rates are measured in liters per second (L/s) or cubic meters per hour (m³/h). Building regulations specify minimum flow rates for plumbing fixtures.
Frequently Asked Questions
What is the flow rate formula?
The volumetric flow rate is calculated using the formula Q = A × v, where Q is the volumetric flow rate in m³/s, A is the cross-sectional area in m², and v is the flow velocity in m/s. The mass flow rate is ṁ = ρ × Q, where ρ is the fluid density in kg/m³.
How do I calculate the flow rate of a pipe?
To calculate the flow rate of a pipe, select the circular shape, enter the pipe inner diameter in meters, and the average flow velocity in m/s. The calculator computes the cross-sectional area A = π × d² / 4 and multiplies it by the velocity to get the volumetric flow rate.
What is the difference between volumetric and mass flow rate?
Volumetric flow rate (Q) measures the volume of fluid passing through a cross-section per unit time (m³/s). Mass flow rate (ṁ) measures the mass of fluid passing per unit time (kg/s). They are related by ṁ = ρ × Q, where ρ is the fluid density.
What units does this flow rate calculator use?
The calculator uses SI units: meters (m) for dimensions, meters per second (m/s) for velocity, square meters (m²) for area, cubic meters per second (m³/s) for volumetric flow rate, and kilograms per second (kg/s) for mass flow rate.
Can I calculate flow rate for rectangular channels?
Yes, select the rectangular or triangular channel shape option. For rectangular channels, enter the width and height in meters. For triangular channels, enter the width and depth. The cross-sectional area is computed based on the selected shape.
Is the Flow Rate Calculator free to use?
Yes, the Flow Rate Calculator is completely free to use with no registration required. You can also share your calculation by copying the URL which saves all your input values.
What is a typical water flow velocity in pipes?
Typical water flow velocities range from 0.5 to 3 m/s in domestic plumbing, 0.5 to 2 m/s in industrial piping, and 1 to 2 m/s in municipal water supply systems. Higher velocities increase friction losses and erosion.
How do I convert m³/s to other flow rate units?
To convert m³/s to liters per second (L/s), multiply by 1000. To convert to gallons per minute (GPM), multiply by 15850.32. To convert to cubic feet per second (cfs), multiply by 35.3147.