Piping
Pipe Flow Rate Calculator
Flow rate in a circular pipe is determined by the cross-sectional area and the average velocity. Given any two of flow rate, velocity, and internal diameter, this calculator solves for the third. No pressure drop, friction, or pipe schedule lookup is included — this is a pure continuity equation calculator.
TypeInteractive calculator — separate from unit conversions
Calculator
Result
Flow rate (Q)0.015708 m³/s
Cross-sectional area (A)0.00785398 m²
Formulas
Cross-sectional area
A = π × D² / 4
Flow rate from velocity
Q = v × A
Velocity from flow rate
v = Q / A
Diameter from flow and velocity
D = √(4Q / (πv))
Diagram
Worked example
A pipe has an internal diameter of 0.1 m (100 mm). Water flows at 2 m/s. What is the flow rate?
- 01A = π × D² / 4 = π × 0.1² / 4
- 02A = 0.00785398 m²
- 03Q = v × A = 2 × 0.00785398
- 04Q = 0.015708 m³/s
Result
The volumetric flow rate is 0.015708 m³/s.
FAQ
Is this a pipe pressure drop calculator?
No. This calculator uses the continuity equation only. Pressure drop requires friction factor, pipe length, roughness, and other parameters that are outside scope.
Does this use pipe roughness or viscosity?
No. Pipe roughness and fluid viscosity are not used. Those are required for friction-based pressure drop calculations.
Does this look up pipe schedules?
No. You must supply the internal diameter directly. Pipe schedule lookup and wall thickness tables are not implemented.
Is this pipe sizing to a design standard?
No. This calculator determines the relationship between flow, velocity, and diameter using the continuity equation. It does not select pipe sizes or apply design velocity limits.