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Gas Pipe Sizing Calculator

Gas systems are primarily used for cooking and heating. ​ Calculate the gas pipe size you need using our gas pipe sizing calculator.

Get accurate results with this simple, yet powerful tool.

Enter fields below to get your results

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Pipe Sizing Calculator

Gas Flow

The flow rate is the volume of gas that passes through an area in a unit of time. It is measured in BTU or mj/hr and is directly proportional to the appliances that are connected.

Pipe Sizing Calculator

Pipe Diameter

There is an inverse relationship between the internal diameter of a pipe and it's velocity. This means that the gas velocity will decrease for a larger size pipe diameter.

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The calculation provides resultes in inches or millimetres for the pipe diameter.

Starting Gas Pressure < 1.5 psi / 10.3 kPa

The following equation can be used to calculate the sizing for a gas pipe:

Formula for Sizing Gas Pipes


  • = Inside diameter of pipe (inches/mm)
  • = Input rate appliance (psi/kPa)
  • = Equivalent pipe length (feet/meters)
  • = Pressure drop [upstream pressure - downstream pressure] (inches of water/kPa)
  • = Natural gas: 0.6094; Undiluted propane: 1.2462
  • = Natural gas: 0.9992; Undiluted propane: 0.9910.

Starting Gas Pressure > 1.5 psi / 10.3 kPa

The following equation can be used to calculate the sizing for a gas pipe:

Formula for Sizing Gas Pipes


  • = Inside diameter of pipe (inches/mm)
  • = Input rate appliance(s) (psi/kPa)
  • = Upstream pressure (psi/kPa)
  • = Downstream pressure (psi/kPa)
  • = Equivalent pipe length (feet/meters)
  • = Pressue drop (inches of water/kPa)
Sizing Gas Pipes Calculator

What is the Gas Pipe Sizing Calculation Used For?

Calculating the sizing of a gas pipe is an essential factor in ensuring the smooth and efficient functioning of any gas-powered systems.

It's primarily used to determine the appropriate diameter of a gas pipe that should be installed in a particular system, be it residential, commercial, or industrial. It takes into account the rate of gas flow, pipe length, pressure drop, and the specific type of gas being used.

Determining the right gas pipe size is critical for a number of reasons:

  • Safety: Improperly sized gas pipes can lead to unsafe conditions. If the pipe is too small, it may not be able to handle the pressure of the gas flow, resulting in leaks or, worse, an explosion. Conversely, a pipe that's too large can cause issues with the gas equipment due to inconsistent or low gas pressure.
  • Efficiency: The right size of pipe ensures that gas devices receive the correct amount of gas to function at their optimum capacity. An undersized pipe can lead to insufficient gas supply, affecting the appliance's performance.
  • Cost-Effectiveness: Correctly sized pipes help in reducing unnecessary expenditure on larger pipes and fittings and lower the risk of costly repairs due to damaged appliances or pipe leaks.
  • Compliance with Regulations: Different regions have specific building and safety codes relating to gas pipe installations. Correct sizing ensures you are in line with these regulations, avoiding legal complications.

h2x for Sizing Gas Pipe Calculations

  • Calculates all of your gas pipe sizes
  • Design a range of plumbing and heating systems
  • Automates all of the calculations based on your layout

h2x is CIBSE-verified design software built to improve the efficiency and quality of your designing process. Read more.

Why Use a Calculator?

There are several benefits of using an online calculator to calculate the sizing of gas pipes, including:

Increased Accuracy

Increased Accuracy:

Determine accurate values by eliminating the possibility of human error when calculating fluid pressure drop by hand.



Saves time by providing quick and easy calcs, eliminating the case to perform complex mathematical calcs manually.

Easy to Use

Easy to Use:

User-friendly and requires no special training or technical knowledge. Just provide the input and read the results.



Can save money by reducing the number of time spent on manual and long calcs, and avoiding costly mistakes.



Want to Learn More About This Topic?

Webinar: Velocity

Learn the fundamentals of velocity calculations and work through real-life scenarios

How to Size Water Pipes

Sizing pipes correctly is critical to the performance of your design - let's do an example together.

Gas Pipe Sizing in 4 Simple Steps

From pressure loss calculations to sizing pipes, we cover it all in our informative guide.

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