Flow rate = volume of fluid ÷ time
Formula: Q = V / t
Use consistent units, such as m³/s, L/min, or gal/min
For mass flow rate, use: ṁ = m / t
For pipe flow, use: Q = A × v
Where A = cross-sectional area and v = fluid velocity
For a circular pipe, use: A = πr²
Substitute area and velocity into Q = A × v
Convert units before calculating if needed
Check that the final unit matches the desired flow rate unit