Pipe Flow Rate Calculator

Pipe Flow Rate is evaluated from Pipe Inner Diameter, Fluid Velocity and Flow Rate. The calculation reports Pipe Cross-Section Area, Flow Velocity and Flow Velocity.

Results

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About the Pipe Flow Rate Calculator

Pipe Flow Rate is treated here as a quantitative relation between Pipe Inner Diameter, Fluid Velocity and Flow Rate and Pipe Cross-Section Area, Flow Velocity, Flow Velocity and Flow Rate.

The calculator uses a multi formula configuration. Each reported value is read as a direct evaluation of the stored rules with the declared field formats and units.

Formula basis:
Q = A x v
A = pi/4 x D^2 (ft^2 if D in feet)
v = Q / A
D = sqrt(4Q / piv)
Conversions: 1 ft^3/s = 448.83 GPM; 1 GPM = 0.002228 ft^3/s

Interpret the outputs in the order shown by the result fields. Optional inputs affect only the outputs that depend on those variables.

Formula & How It Works

The calculation applies the following relations exactly as recorded in the metadata:

Q = A x v
A = pi/4 x D^2 (ft^2 if D in feet)
v = Q / A
D = sqrt(4Q / piv)
Conversions: 1 ft^3/s = 448.83 GPM; 1 GPM = 0.002228 ft^3/s

Each output field is produced by substituting the supplied inputs into the relevant relation and then applying the declared rounding or text format.

Worked Examples

Example 1: Residential Water Service Line

Inputs

diameter_in: 1 flow_gpm: 15
Pipe Cross-Section Area: 0.7854 in^2. Flow Velocity: 367.648 ft/s. Flow Velocity: 250.67 mph. Flow Rate: 15 GPM. Flow Rate: 2.0052 ft^3/s. Required Diameter: 1 in

With Pipe Inner Diameter = 1 and Flow Rate = 15 as the stated inputs, the result is Pipe Cross-Section Area = 0.7854 in^2, Flow Velocity = 367.648 ft/s and Flow Velocity = 250.67 mph. Each value corresponds to the declared output fields.

Example 2: Fire Sprinkler System Header

Inputs

diameter_in: 4 velocity_fps: 6
Pipe Cross-Section Area: 12.5664 in^2. Flow Velocity: 6 ft/s. Flow Velocity: 4.09 mph. Flow Rate: 3.92 GPM. Flow Rate: 0.5236 ft^3/s. Required Diameter: 4 in

With Pipe Inner Diameter = 4 and Fluid Velocity = 6 as the stated inputs, the result is Pipe Cross-Section Area = 12.5664 in^2, Flow Velocity = 6 ft/s and Flow Velocity = 4.09 mph. Each value corresponds to the declared output fields.

Example 3: Irrigation Main Line Sizing

Inputs

velocity_fps: 5 flow_gpm: 50
Flow Velocity: 5 ft/s. Flow Velocity: 3.41 mph. Flow Rate: 50 GPM. Flow Rate: 6.684 ft^3/s. Required Diameter: 15.656 in

With Fluid Velocity = 5 and Flow Rate = 50 as the stated inputs, the result is Flow Velocity = 5 ft/s, Flow Velocity = 3.41 mph and Flow Rate = 50 GPM. Each value corresponds to the declared output fields.

Example 4: Municipal Water Main Velocity Check

Inputs

diameter_in: 8 flow_gpm: 800
Pipe Cross-Section Area: 50.2655 in^2. Flow Velocity: 306.373 ft/s. Flow Velocity: 208.89 mph. Flow Rate: 800 GPM. Flow Rate: 106.9444 ft^3/s. Required Diameter: 8 in

With Pipe Inner Diameter = 8 and Flow Rate = 800 as the stated inputs, the result is Pipe Cross-Section Area = 50.2655 in^2, Flow Velocity = 306.373 ft/s and Flow Velocity = 208.89 mph. Each value corresponds to the declared output fields.

Common Use Cases

  • Find water velocity in a 2-inch pipe at given flow rate
  • Calculate required pipe size for a target flow rate
  • Determine GPM flow rate from pipe diameter and velocity