Pipe Flow Rate Calculator
Calculate volumetric flow rate, flow velocity, Reynolds number, and required pipe diameter. Essential for pump selection, pipe sizing, and hydraulic system design.
Pipe Flow Calculations
Q = V × A — Calculate volumetric flow rate
Use internal (bore) diameter, not OD
Recommended: 1.5–2.5 m/s for water
Find Piping Products
Recommended Velocities
Pipe Flow Rate Calculator: Engineering Guide
This pipe flow rate calculator is an essential tool for engineers designing fluid distribution systems, selecting pumps, or troubleshooting existing pipelines. Using the fundamental relationship Q = V × A (flow rate equals velocity times cross-sectional area), you can instantly calculate volumetric flow rates in m³/h, GPM, or L/s.
The Reynolds number calculator determines whether your pipe flow is laminar (Re < 2,300) or turbulent (Re > 4,000), which affects friction factor selection, pressure drop calculations, heat transfer, and mixing characteristics in process applications.
Key Calculations
- Volumetric flow rate (m³/h, GPM, L/s)
- Average flow velocity (m/s, ft/s)
- Reynolds number and flow regime
- Darcy friction factor (Colebrook-White)
- Required pipe diameter for design velocity
- Standard pipe size selection guide
Applications
- Pump selection and system design
- Mining slurry pipeline design
- Water reticulation and distribution
- Chemical process piping
- HVAC chilled and hot water systems
- Fire protection sprinkler systems
Pipe Flow Formulas
Volumetric Flow Rate
Q = V × A = V × π × (D/2)²
Q in m³/s, V in m/s, D in m
Flow Rate Conversions
1 m³/h = 4.403 GPM = 16.67 LPM
1 L/s = 3.6 m³/h = 15.85 GPM
Cross-Sectional Area
A = π × D² / 4
D = internal pipe diameter (m)
Reynolds Number
Re = V × D / ν
ν = kinematic viscosity (m²/s)
Required Diameter
D = √(4Q / (π × V))
Rearranged from Q = V × A
Friction Factor (Laminar)
f = 64 / Re
Valid for Re < 2,300 only
Standard Pipe Sizes Reference (SANS 62 / ISO 4200)
| Nominal Size (DN) | OD (mm) | Wall Thickness (mm) | Internal Diameter (mm) |
|---|---|---|---|
| DN25 | 33.7 | 2.6 | 28.5 |
| DN40 | 48.3 | 2.6 | 43.1 |
| DN50 | 60.3 | 2.9 | 54.5 |
| DN65 | 76.1 | 2.9 | 70.3 |
| DN80 | 88.9 | 3.2 | 82.5 |
| DN100 | 114.3 | 3.6 | 107.1 |
| DN150 | 168.3 | 4.0 | 160.3 |
| DN200 | 219.1 | 4.5 | 210.1 |
| DN250 | 273.0 | 5.0 | 263.0 |
| DN300 | 323.9 | 5.6 | 312.7 |