Gas Pipe Sizing Calculator 4+

Mr Combi Training

Designed for iPad

    • £4.99



A study carried out by Worcester Bosch Group's technical support team found that the most common cause of a boiler installation problem was from incorrectly sized gas pipes. When fitting a new boiler, often the existing pipes should be replace for larger ones due to the increased output. Smaller pipes will mean the boiler is running at a lower power and can cause an increase in carbon monoxide levels.

The Gas Pipe Sizing Calculator is an extremely easy to use app that will help you to select the right size pipes for installations using copper (up to 108mm), steel (up to 300mm) and PE (up to 315mm) pipes of sections up to 250m (820ft) in length.

To carry out a calculation simply select the gas type, enter the appliance heat input, enter the pipe length, the number of high or low loss fittings (guidance is given in the app), select the type of pipe and then press the 'Calculate' button.

The results will show the total equivalent length, the minimum pipe diameter (metric) that should be used and the pressure drop for that section of pipe.

For multiple appliances each section should be calculated in turn and the kW inputs for the appliances in each section added together for each calculation.

The maximum pressure drop from each appliance to the meter should be no more than 1 mbar for natural gas or 2.5 mbar for butane or propane. Adding all drops together using the minimum pipe diameters may cause this to be exceeded. Where possible, the results will also calculate the drop if the next larger size pipe diameter is selected on a section, this should help to ensure the right sizes are used throughout the whole circuit.

Please note: This app is designed mainly for the UK so supports metric pipe sizes only.

What’s New

Version 2.7

- Upgrade the app 
- Remove some sections.

Ratings and Reviews

4.6 out of 5
5 Ratings

5 Ratings

cmgm1 ,


Does exactly what it says on the can. Ideal quick calculator without getting bogged down with complicated charts.
Another reviewer commented that you’d have to know exactly what you’re doing to use this app.......I should hope so, you want non gas registered people installing your gas supply pipe work?????

Bowl o rice ,

Very easy to use

Very quick and easy, accurate enough an who needs more than 35mm? More than adequate for normal domestic installs

Unhappy GasmanNI ,

Basic pipe calculator

Basic straight length calculator where it is up to the user to calculate effective pipe length and make their own allowance for bends and fittings.

The user will need to do a carcass drawing and note pressure drop and check index runs do not exceed 1mb drop on nat gas.

Tends to allow pressure drop of up to 0.5mb on each length and would be useful if it calculated down to .15 drop as if you various branches on larger pipe work.

This needs to be used by someone that knows exactly what they are doing.

Have used others where the carcass could be input inc branches and end loads and then changes made automatically resize whole project.

App Privacy

The developer, Mr Combi Training, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary based on, for example, the features you use or your age. Learn More


  • Family Sharing

    Up to six family members can use this app with Family Sharing enabled.

More By This Developer

Gas Rate Calculator & Guide
Heatloss Calculator & Guide
Gas Ventilation Calculator UK
Wiring & Controls - Diagrams
Fault Finding & Multimeters
Boiler Fault Codes

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