H2X Tools

Pipe Velocity Calculator

Water flow rates are measured by the volume of water passing per unit of time. The water flow rate, along with the pipe diameter can be converted to a velocity using a pipe velocity calculator.


What is the Pipe Velocity Calculation Used For and Why is it Important?

Pipe velocity is the speed at which fluid flows through a pipe and is usually measured in terms of m/s or ft/s.

It’s important to know what your pipe velocity is because it relates closely to frictional losses. The higher the velocity of a fluid, the higher the friction loss is.

High friction loss affects the pump’s performance and other related equipment, which might mean you have to opt for bigger pumps.

Larger pumps and equipment can increase the capital cost of the building and also increase the operational cost to run the building. So this calculation is vital when designing a system.

pipe velocity calculator

Pipe Velocity Calculator

As the calculation can be measured in terms ft/second and m/second, there are two different calculation methods to establish pipe velocity:

Imperial pipe velocity calculator

The Imperial Equation

The following equation can be used to calculate the pipe velocity:

v=0.0408 Velocity Calculator free to use h2x engineering

Components of the Equation

V = Water velocity inside the pipe (ft/second)

Q = Water flow rate inside the pipe (GPM)

D = Pipe inside diameter (inner diameter) (in)

The Metric Equation

The following equation can be used to calculate the pipe velocity:

v=1.274 Velocity Calculator free to use h2x engineering

Components of the Equation

V = Water velocity inside the pipe (m/second)

Q = Volume flow (m³/second)

D = Pipe inside diameter (inner diameter) (m)


Pipe Diameter and Water Flow Rate

The water flow rate


The pipe diameter

Water Flow Rate

The flow rate of the fluid is the volume of fluid that passes through an area in a unit of time. It is measured in m³/s, GPM, or l/s and is directly proportional to the pipe flow velocity.

Pipe Internal Diameter

There is an inverse relationship between the internal diameter of a pipe and the pipe velocity. This means that the water velocity will increase as the pipe diameter decreases

Using Our Pipe Velocity Calculator

This free spreadsheet contains the pipe velocity formula that is used for the H2X calculations. The spreadsheet calculates the water velocity if you have the following variables available:

Flow Rate

Pipe Diameter

pipe velocity free spreadsheet

All pipe materials and sizes available in H2X have been verified against the above spreadsheet.

You can check the verified results below.


There can be a difference between the values spreadsheet and values in the H2X result due to the rounding up of multiple decimal places within the calculation. The difference generally occurs by the third decimal place in the flow velocity result.

How Can H2X Simplify Manually Calculating Velocity?

Besides the fact that manually calculating pipe velocity is a time-consuming process, any manual calculation opens up the doors for human error.

The objective behind creating the H2X software solution was to use modern technology combined with recognised methods of plumbing engineering to automate the entire plumbing design workflow, including these calculations, so you can save hundreds of hours designing each project while reducing errors, rework, and costs.

Using H2X, you won’t need to use a manual pipe flow calculator as the process is automated.

The process is you follow when using H2X is:

Set the parameter for maximum velocity

Draw the total pipe layout

The flow rate is automatically calculated based on how many fixtures are connected to the pipe.

The pipe size is automatically calculated using the mass flow rate and maximum velocity parameter.

The pressure drop can then be automatically calculated


This depends on variables:

  • The local standard

For example, pipes are generally designed to higher velocities in the USA compared to the UK

  • The pipe material

For example, stainless steel pipes can generally be designed to higher velocities than copper pipes

  • If the pipe is above a habitable space

For example, if the pipe is above a room such as a bedroom, the pipe velocity should be kept low to avoid undue noise

  • The application

For example, pipes containing hot water in recirculating systems should be designed to a lower velocity than cold water pipes

Typical water velocity in a pipe is generally between 0.7-2.4 m/s. Typical velocities are usually:

Cold water velocity - 1.5-2.4m/s or 5-8 ft/s

Hot water flow velocity - 1.2-1.5m/s or 4-5 ft/s

Hot water return velocity - 0.7-1m/s or 2-3 ft/s

Velocities should generally not go lower than 0.7m/s as this is required to maintain a self-cleansing velocity. For example, if liquids contain solid particles, engineers try to achieve a higher velocity so that the heavy particles in the liquid don’t settle and cause blockage in the pipe.

See What H2X Can Do

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