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

This is now a universal app that works on both the iPhone and iPad and sizes the screen size accordingly.

You can specify the total gas flow in ft^3/hr (m^3/hr), the upstream pressure (psig or kPa), and one of either downstream pressure (psig or kPa), 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, the upstream pressure, and one of either downtream pressure 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.

This 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.

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 3.6

1. Fixed issue with not displaying properly in iOS 13 "dark mode"

Ratings and Reviews

5.0 out of 5
3 Ratings

3 Ratings

Mechengineer1000 ,

Easy to use, but I wish it had a little more

This app is very easy to use. I simply slide the input controls, and it updates the results. For example, I can slide the gas flow control to quickly change the cubic ft/hr of gas flow to see how it affects the internal diameter and downward pressure. I can also slide the upstream pressure input slider to see how it affects results.

I wish it allowed you to store info for each "pipe run" so I could build a simple pipe system to see the entire pressure loss, etc. Also, I wish you could email or upload the results somewhere so I could easily plug them into my spreadsheet. Maybe the next version.

Great work, though.

LZ2124 ,

I like it a lot

Carmel has really done a nice job designing this and other apps. So simple yet contains lots of good functionality to truly make it useful in the field and office.

I'm always a little skeptical of these engineering apps because you never know how well they really work on these little iPhone screens, but sometimes simple is better.

So far, the results appear to be quite accurate and even the fitting equivalent lengths for the different pipe materials look correct.

I use this app a couple times a week so it's more than paid for itself.

Hvacguy100 ,


This is the only high-pressure gas piping software app I've found on the Appstore. I'm in the field a lot and this is perfect for doing quick rule-of-thumb calcs on some of the process piping that I often run across. I like that I do not have to input a value into the box, just slide the control. Great effort!


Carmel Software Corporation
17 MB

Requires iOS 11.0 or later. Compatible with iPhone, iPad, and iPod touch.



Age Rating


  • Family Sharing

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

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