# Duct Calculator — Ductulator & Duct Sizer

> HVAC duct sizing and performance calculator for engineers and contractors. (iPhone/iPad app by Pheinex, LLC.)

- Source: https://appshunter.io/ios/app/duct-calculator/id1078238132 (this page in markdown: same URL + `.md`)
- Developer: [Pheinex, LLC](https://appshunter.io/developer/996932317)
- Category: Utilities, Business
- Price: $19.99
- Rating: 4.50/5 from 188 App Store ratings · 17 written reviews indexed
- Age rating: 4+
- Requires: iOS 15.0 · 2 MB
- Languages: American English
- Released: 2016-04-05
- Data updated: 2026-08-13
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/duct-calculator/id1078238132/reviews.md

## What is Duct Calculator?

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

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.

PERFORM QUICK AND ACCURATE CALCULATIONS:

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.

HOW TO USE:

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.

Output:

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

NOTES:

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 professional.

## Key features

- Size round and rectangular ductwork
- Adjust airflow, diameter, width, and height
- Direct number entry for precision
- Lockable dimensions for 'what-if' scenarios
- Live update of calculated values
- Outputs velocity and pressure drop
- Supports IP and SI units

## Recent user reviews (10 of 17)

All indexed reviews: https://appshunter.io/ios/app/duct-calculator/id1078238132/reviews.md

### 3/5 — Where’s the option for flex duct?

*2024-02-08*

Not happy with my purchase

### 5/5 — GREAT APPLICATION

*2023-12-02*

I've been using it for many years, my go to every day.

### 1/5 — Really mot good app .

*2023-07-05*

Calculation are not acure , not integral proximity in calculations

### 3/5 — Subscription

*2023-05-16*

Do I have to pay monthly subscription for this app or just one time pay at the start?

### 4/5 — Almost perfect… but not quite there.

*2023-03-17*

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.

### 5/5 — Better than cardboard Ductulator

*2022-05-27*

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.

### 1/5 — Not accurate

*2022-05-03*

I was trying to find an app for the convenience of not carrying several sliders around in a bag, I just have everything in one place.  But the interface isn’t easy to use or quick, and non of the numbers are adding up to any duct calculator I have or have access to.  I can’t trust any of the numbers and I can’t use something if I can’t trust it.

### 5/5 — Great app.

*2021-04-22*

I really like the dial format for selecting duct sizes.

### 5/5 — A must have

*2020-12-20*

This is an excellent tool for on the job calculation. It’s a must have.

### 5/5 — Problems since update

*2020-09-21*

Latest update seems to be causing velocity errors, 132 l/s on a duct size of 200mm dia should jot be coming up as over 40m/s ?? Please can this be rectified as was a great app before the update

**Developer response:** A fix for the velocity display issue has been submitted and approved by Apple. The update should be rolling out soon.

You can contact us directly here: https://www.pheinex.com/contact/

## Frequently asked questions about Duct Calculator

### What does the Duct Calculator app do?

The app is designed for HVAC engineers, designers, and contractors to quickly and accurately size new ductwork or calculate the performance of existing ducts. It allows for precise calculations of duct dimensions, airflow, velocity, and pressure drop.

### How can I use the Duct Calculator app?

You can use the app by adjusting airflow and duct dimensions (diameter, width, height) using intuitive sliders for quick calculations, or by entering exact numbers directly for maximum precision. Specific dimensions can be locked to perform 'what-if' analyses.

### Is the Duct Calculator app free to use?

Yes, based on the provided information, the app is available for free. There are no mentions of in-app purchases or subscription models.

### What types of ductwork can be sized with this app?

The app supports sizing for both round and rectangular ductwork. It provides equivalent round and rectangular duct sizes, as well as outputs for velocity and pressure drop for both types.

### What units of measurement does the app support?

The app is designed to work with both Imperial (IP) and International System of Units (SI). This allows users to perform calculations according to their preferred measurement standards.

## Version history (last 5 releases)

### 1.8.0 — 2024-02-09

Bug fixes and improvements.

### 1.7.0 — 2024-01-03

Bug fixes and improvements.

### 1.6.1 — 2022-09-15

Bug fixes

### 1.6.0 — 2022-09-13

Updates for iOS 16 and the latest phones.

### 1.5.2 — 2021-04-23

Bug fixes and improvements.

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## More apps by Pheinex, LLC

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All apps by Pheinex, LLC: https://appshunter.io/developer/996932317

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-13.*