Duct Calculator 4+

Ductulator & Duct Sizer

Pheinex, LLC

    • 5.0 • 2 Ratings
    • $4.99


The Duct Calculator App is a modern take on a the classic duct sizing wheel. HVAC engineers, designers and contractors quickly and accurately size a new duct or calculate the performance of an existing duct on your Mac.

Size both round and rectangular ductwork with the ease of a traditional Ductulator. Adjust the airflow, diameter, width or height sliders with your thumbs. Get maximum precision by entering numbers directly into the the calculator. Lock friction rate, diameter or width or height to make the calculations you need for your design.

Live update of the calculated values allows you to see the impact of the changes immediately.

Outputs velocity for both round and rectangular ducts.


Enter the airflow and sizes in directly as numbers for maximum precision.
- or -
Use the airflow and size sliders for quick calculations.

Shows live equivalent round/rectangular duct sizes.

Specific dimensions can be locked to allow specific what-ifs to be quickly calculated.

Works for both IP and SI units.

You can select from a range of duct roughness categories.

Designed to allow quick calculations anywhere, anytime, it is ideal for the HVAC designer or contractor.


Locking Dimensions:

The lock symbols to the right of the duct dimensions indicate if that particular dimension is locked when calculating new equivalent values when a dimension is updated.

The Diameter can be locked or unlocked.

The Width or Height can be locked, but not both.

Using the Sliders:

Move the sliders for Airflow, Duct Diameter, Width and Height up and down to match the desired duct size to calculate velocity and pressure drop for.

The Diameter, Width and Height will change such that the equivalent size is shown:

Changing the diameter will updated either the equivalent Width or the Height, depending on which dimension is unlocked.

Changing the Width or Height will update the equivalent Diameter if it is unlocked, or the other rectangular duct dimension of the Diameter size is locked.

Direct Entry:

The values for Airflow, Diameter, Width and Height can be directly edited in the text boxes to allow quick entry of exact numbers.

Invalid entries will generate an error message, and must be corrected prior to the calculations updating.


The values for the calculated Velocity for Round Duct and Rectangular Duct are shown, as is the Pressure Drop per Length value.


We would very much like your feedback!
Suggestions, complements, complaints, bug reports etc.:


If you like this app, please do not forget to rate it in the App Store!


This application (App) is provided for use by qualified HVAC engineers and designers in the design of air handling systems and is not a substitute for appropriate design services. When in doubt, contact a design

What’s New

Version 1.6.1

Bug fixes

Ratings and Reviews

5.0 out of 5
2 Ratings

2 Ratings


Almost perfect… but not quite there.

This thing is great. only 2 things would make it perfect. 1) Flex duct sizing. 2) multiple friction rate fields, so you can select both your return AND supply friction rates at the same time and see output of both. plus have those fields be lockable so you can’t change them by accident. If these changes were made, I would buy this AGAIN and likely so would every consultant in my company.


Better than cardboard Ductulator

It’s a little difficult to get used to the way things work at first, having only used the rotating cardboard Trane ductulators in the past, but once you get used to it it is much more accurate and far easier to obtain correct sizing for very specific lengths and widths of duct.

Marty731959 ,

Great app.

I really like the dial format for selecting duct sizes.

App Privacy

The developer, Pheinex, LLC, 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, for example, based on the features you use or your age. Learn More


  • Family Sharing

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

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