# Pipe Velocity Calculator

URL: https://speedycalculator.com/calculators/physics/pipe-velocity/
Last updated: 2026-10-30

> The pipe velocity calculator finds the average flow velocity in a pipe from the volumetric flow rate and the inner diameter.

## Inputs

- Flow rate Q (L/s, m³/s, m³/h, L/min, US gpm, ft³/s)
- Inner diameter d (mm, cm, m, in, µm)

## Results

- Flow velocity v
- Cross-section area

## Formula

```
v = Q / (π·d²/4)
```

## Explanation

Keeping velocities in the right range avoids noise, erosion and water hammer in pressurised pipes (usually 1–3 m/s for water) while preventing sediment build-up in drains.

### How to use the Pipe Velocity Calculator

- **Flow rate Q**
- **Inner diameter d**

Results update as you type, every field has its own unit menu, and everything is calculated in your browser.

### How it works

Enter the flow rate and the pipe's inner diameter.

### Inputs explained

FieldWhat to enterFlow rate QUnits: L/s, m³/s, m³/h, L/min, US gpm, ft³/sInner diameter dUnits: mm, cm, m, in, µm

### What each result means

- **Flow velocity v** = [Flow rate Q]÷(pi×[Inner diameter d]^2÷4)
- **Cross-section area** = pi×[Inner diameter d]^2÷4

### Example values

How the main result changes when **Flow rate Q** changes and everything else stays at the example values above:

Flow rate Q (L/s)Flow velocity v (m/s)10.79581.51.193721.59152.51.989432.387343.1831

## Worked example

Inputs — Flow rate Q: 2 L/s; Inner diameter d: 40 mm.

Results — **Flow velocity v = 1.59155 m/s**; Cross-section area = 12.56637 cm².

## Key terms

- **Continuity**: Flow rate = area × velocity.

## FAQ

**What velocity is recommended for water pipes?**
About 1–2.5 m/s for supply lines.

**Why avoid high velocities?**
Noise, erosion and pressure surges.

**Does the pipe material matter?**
Not for velocity – only for friction.

**How does diameter affect velocity?**
Halving the diameter quadruples the velocity.


## Sources

- [OpenStax – University Physics Volume 1](https://openstax.org/details/books/university-physics-volume-1)
- [The Engineering ToolBox](https://www.engineeringtoolbox.com/)