The "HVAC Pipe Sizer - Gas Low" application allows you to quickly size a simple low pressure (< 1.5psi) gas piping system by inputting a number of piping and gas properties.

You can specify the total gas flow in ft^3/hr (m^3/hr) and one of either pressure drop (in. wg or Pa), pipe internal diameter (inches) or gas velocity (ft/s) parameters. The results include both the exact and nominal pipe diameters and the calculated velocity and total pipe equivalent length. If you are analyzing an existing pipe system, there is an option to input the existing pipe internal diameter and one of either pressure drop or gas velocity parameters to derive the calculated gas flow and other remaining properties.

You can specify additional parameters such as the type of gas, various properties of the gas, the pipe material type, the total length of pipe, quantities for up to 11 different types of pipe fittings, and much more. You can also choose to display values in either english or metric units.

This application includes built-in pipe fitting equivalent length and nominal pipe sizing tables for a wide variety of pipe material types and diameters.

The "HVAC Pipe Sizer - Gas Low" application uses slider controls that allow you to quickly increment or decrement the input values and immediately observe the calculated results. You can also manually input exact values.

All values can be displayed in English (IP) and Metric (SI) units.

This app now includes the HVAC Equipment Locator. Click here for details:

This application was designed by Carmel Software Corporation, a leader in HVAC design software since 1995. In fact, Autodesk (the makers of AutoCAD) acquired our load calculation software and incorporated it into their leading 3D modeling software called Revit.

We also offer the following additional applications for the iPhone/iPad:

1. HVAC Duct Sizer
2. HVAC Pipe Sizer – Gas Low Pressure
3. HVAC Pipe Sizer - Gas High Pressure
4. HVAC Pipe Sizer – Liquid
5. HVAC Pipe Sizer – Steam
6. Steam Tables
7. Psychrometric Plus
8. Psychrometric LT
9. HVAC Pipe Sizer Plus
10. HVAC Pipe Sizer Gas Plus
11. HVAC Toolkit
12. HVAC Toolkit Ultimate
13. HVAC Residential Load Calcs
14. HVAC Load Plus
15. HVAC Equipment Locator
16. ASHRAE Duct Fitting Database
17. ASHRAE 62.1 Ventilation Load Calcs
18. HVAC Psych HD
19. HVAC ResLoad-J
20. HVAC Residential Load Calcs HD

What's New

Version 3.0

1. Optimized for iOS 11
2. Optimized for all iPhone and iPad screen sizes including the iPhone X
3. Updated UI
4. Updated help

Ratings and Reviews

Lots of functionality


This app has lots of great functionality. Allows me to input gas flow then either input pressure drop, diameter, or velocity. Also, allows me to size according to diameter and pressure drop to see what the expected flow rate is.

I also like how it stores all my results, so when I close it and come back to it later on, the same values are there.

Very useful.

Useful for field work


Great little app for approximating low pressure gas pipe sizes out in the field. I often go to homes to diagnose heating issues and want to make sure the gas pipes are the correct size (you won't believe how many are over or under sized). Anyway, this app helps me diagnose those issues. I highly recommend it.


Carmel Software Corporation
18.9 MB
Requires iOS 7.0 or later. Compatible with iPhone, iPad, and iPod touch.
Age Rating
Rated 4+
© 2018 Carmel Software Corporation. All Rights Reserved.


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

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