Pipe Velocity Calculator — Accurate Fluid Flow Rate & Pipe Sizing

Pipe Velocity Calculator

Calculate fluid velocity in pipes, determine flow rates, and size pipes correctly for plumbing, HVAC, or irrigation systems. Get precise fluid dynamics calculations.

Step 1: Pipe Dimensions

Pipe Measurements

Accurate pipe dimensions and flow rates are crucial for calculating fluid velocity and pressure drop. Internal diameter is most important for velocity calculations.

Step 2: Fluid Properties

Fluid Properties

Fluid viscosity and density affect flow velocity and pressure drop. Water at 60°F has a viscosity of approximately 1.12 cP and density of 62.4 lb/ft³.

Pipe Velocity Calculation Results

Summary
Flow Analysis
Pressure Drop

Fluid Velocity in Pipe

5.1 ft/s
Flow Type: Transitional
Flow Rate
50 GPM
Reynolds Number
12,450
Pipe Area
3.14 in²
Recommended Velocity
2-5 ft/s

Flow Analysis & Reynolds Number

Velocity (ft/s)
5.1
Feet per Second
Velocity (m/s)
1.55
Meters per Second
Reynolds Number
12,450
Dimensionless
Flow Type
Transitional
Transitional Flow

Understanding Flow Types

Laminar Flow (Re < 2,000): Smooth, orderly fluid motion with parallel layers. Transitional Flow (2,000 < Re < 4,000): Mix of laminar and turbulent characteristics. Turbulent Flow (Re > 4,000): Chaotic, irregular fluid motion with eddies and vortices.

Velocity Guidelines for Different Applications

Application Recommended Velocity Maximum Velocity
Water Supply (Main) 3-5 ft/s (0.9-1.5 m/s) 8 ft/s (2.4 m/s)
Water Supply (Branch) 2-4 ft/s (0.6-1.2 m/s) 6 ft/s (1.8 m/s)
Hydronic Heating 2-4 ft/s (0.6-1.2 m/s) 5 ft/s (1.5 m/s)
Industrial Process 3-7 ft/s (0.9-2.1 m/s) 10 ft/s (3.0 m/s)

Pressure Drop Calculation

Pressure Drop (Total)
4.2 psi
Pressure Drop per 100 ft
2.1 psi/100ft
Friction Factor
0.021
Head Loss
9.7 ft

Pressure Drop Formula (Darcy-Weisbach)

ΔP = f × (L/D) × (ρ × v²/2)

Where: f = friction factor (dimensionless), L = pipe length (ft), D = pipe diameter (ft), ρ = fluid density (lb/ft³), v = fluid velocity (ft/s). This equation calculates pressure drop due to friction in a pipe.

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