Online Tool Store
Pipe Volume & Flow Calculator
Enter a pipe's diameter and length to calculate its internal volume, and enter a flow velocity to calculate the resulting flow rate.
This works right here on your device — nothing gets sent out.
Cross-sectional area
—
cm²
Volumetric flow rate
—
liters/min
Flow rate (other units)
—
Volume in pipe (given length)
—
liters
How it works
- Enter the pipe's internal diameter and the fluid's average flow velocity.
- The calculator computes the pipe's cross-sectional area and multiplies it by velocity to get volumetric flow rate.
- Optionally enter a pipe length to also see the total internal volume the pipe holds.
The formula
A = π × (d ÷ 2)²
Q = A × v
Example: a 50 mm (0.05 m) internal diameter pipe with a flow velocity of 1.5 m/s has an area of π × 0.025² ≈ 0.001963 m², giving a flow rate of about 176.7 liters per minute.
FAQ
What's the formula for flow rate through a pipe?
Volumetric flow rate Q equals the pipe's cross-sectional area (A = πr²) multiplied by the fluid's average velocity: Q = A × v. This calculator takes your diameter and velocity, computes the area, and multiplies them, converting the result into several common flow-rate units.
Does this account for friction or pipe roughness?
No — this is a straightforward Q = A × v calculation assuming you already know (or have measured/estimated) the average flow velocity. Determining that velocity for a real system typically requires accounting for pressure, pipe roughness, and fittings (e.g. via the Darcy-Weisbach equation), which is outside this calculator's scope.
Why does it ask for internal diameter, not outer diameter?
Flow only moves through the pipe's internal (bore) diameter — the outer diameter includes wall thickness that doesn't carry fluid. Using outer diameter would overstate the cross-sectional area and therefore the flow rate.
How we compare
| Feature | Online Tool Store | Manual calculation with a calculator app | Engineering reference tables |
|---|---|---|---|
| Converts to multiple flow units instantly | ✓ | ✗ | ✗ |
| Also computes pipe internal volume | ✓ | ✗ | ✗ |
| Free, no sign-up | ✓ | ✓ | ✓ |
A reference table gives you the formula; this does the arithmetic and unit conversion instantly, in liters/min, US gpm, and m³/h at once.