HVAC Duct Sizer voted favorite mobile app by readers of Contracting Business magazine.

The HVAC Duct Sizer app is the #1 selling duct sizing application for the Apple iPhone and iPad. Tens of thousands of happy users have downloaded this useful application for performing quick and simple duct sizing analysis.

The HVAC Duct Sizer is a universal duct sizing app so that it works on both the iPhone and iPad and adjusts its screen size accordingly.

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

Just a couple of comments from our users:

"I'll be presenting your iPhone program to my HVAC class as an easy compact tool to have in hand when making sales and service calls." - R. Black

"I like this app and use it daily" - V. Joe

The Duct Sizer application allows you to quickly size one HVAC duct run or a range of duct sizes using the constant friction method. Think of this application as a digital version of the classic Trane Ductulator.

In the "Size by Airflow" mode, you can specify the total airflow in CFM (or L/s), the aspect ratio and one of either the velocity of air or the friction loss per 100 feet (30 meters). The results include both the exact and rounded height and width (or diameter) dimensions and the calculated velocity and friction loss.

In the "Size by Dimensions" mode, you can analyze an existing duct system. There are options to input the existing duct dimensions and one of either the airflow or velocity values to derive the calculated duct friction loss.

In the "Range of Duct Sizes" mode, you can specify minimum and maximum friction loss and airflow values to display a range of duct sizes that fall in between the friction loss bounds.

You can specify additional parameters such as the duct shape (rectangular, round, or oval), the air temperature and the air pressure. You can also choose to display values in either English (IP) or Metric (SI) units.

This application uses slider controls that allow you to quickly increment or decrement the input values and immediately observe the calculated results.

This app now works on your iPhone and iPad and adjusts its screen size accordingly.

Finally, you can email all of the inputs and results from all 3 input modes to perform further analysis using your desktop computer. The email includes HTML text and a .CSV attachment that can be imported into any popular spreadsheet.

The "HVAC Duct Sizer" 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. In addition, we developed a number of customized apps for ASHRAE, DNV GL, and other organizations.

This app now includes the HVAC Equipment Locator which allows you to keep track of all of your equipment and store it in the cloud. Click here for details:

We also offer the following additional apps for the iPhone and iPad:

1. HVAC Residential Load Calcs for iPhone and iPad
2. HVAC Quick Load Plus
3. HVAC Quick Load
4. HVAC Toolkit
5. HVAC Pipe Sizer – Gas Low Pressure
6. HVAC Pipe Sizer - Gas High Pressure
7. HVAC Pipe Sizer – Liquid
8. HVAC Pipe Sizer – Steam
9. Steam Tables
10. Psychrometric Plus
11. Psychrometric LT
12. HVAC Pipe Sizer Plus
13. HVAC Pipe Sizer Gas Plus
14. HVAC Toolkit Ultimate
15. HVAC Equipment Locator
16. HVAC ResLoad-J
17. HVAC Psych HD

What’s New

Version 5.6

1. Updated the app launch screen per new Apple iOS guidelines.
2. Updated the help.

Ratings and Reviews

3.2 out of 5
6 Ratings

6 Ratings

Manical1 ,

Good app, needs iPod touch support

I bought this app for my iPhone. Very handy and good for duct sizing in the field. Next iteration might want to tabulate duct runs for friction loss.

I hope the author of the program reviews the abilty for it to load on an iPod touch. When I tried to buy it for the touch it said that the application won't work on the touch because it needed a microphone. Unless there is a sound or db meter application I don't see why this is the case.

I also bought the sister app for pipe siZing. Good little app also, hope the author continues to write and develop software for HVAC. Maybe pyschtometric app?

Jimmy Teets ,

Great duct sizer

I’m an HVAC engineer and I use this at work almost every day. It’s a great way to quickly size a run of duct and easily switch between duct types.

EQJ79 ,

high quality accuracy.

Very accurate and useful. Relatively easy to use if you know how to properly size ducts. The only problem with the app is after you enter a value, the screen stops scrolling up and down so you can't see the results. You have to back out to the main menu then re-select the category (i.e. Size by airflow) to see the answer.


Carmel Software Corporation
18.4 MB

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



Age Rating
In-App Purchases
  1. HVAC Equipment Locator $9.99


  • Family Sharing

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

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