# Duct Calculator: HVAC Sizing — HVAC duct sizing & airflow

> HVAC duct sizing & airflow (iPhone/iPad app by Vladimir Lukashov.)

- Source: https://appshunter.io/ios/app/duct-calculator-hvac-sizing/id6789039757 (this page in markdown: same URL + `.md`)
- Developer: [Vladimir Lukashov](https://appshunter.io/developer/6783697231)
- Category: Utilities, Productivity
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 17.0 · 8 MB
- Languages: American English
- Released: 2026-07-15
- Data updated: 2026-09-02
- User reviews in markdown: https://appshunter.io/ios/app/duct-calculator-hvac-sizing/id6789039757/reviews.md

## What is Duct Calculator?

The digital ductulator. Equal-friction duct sizing in your pocket, no cardboard slide rule.

Type in the airflow and get the duct size. Or type in a duct that's already there and find out what it actually carries. Every calculation runs on the device, with no account and nothing to load.

Every subscription starts with a free trial, so you can put it through a real job before you pay for anything. After the trial Ductulator needs a subscription, and the tools below are what it unlocks. Cancel anytime in Settings.

WHAT YOUR SUBSCRIPTION UNLOCKS

SIZE A NEW DUCT
- The exact diameter the airflow needs, plus the nearest standard round size
- Fix one side of a rectangular duct and get the matching other side
- Equivalent round diameter (Huebscher), to cross-check against round runs
- Air velocity, flagged when it runs above the residential guide

CHECK A DUCT THAT'S ALREADY THERE
- Type in a round diameter, or a width and a height
- Read back its velocity, its friction rate, and the airflow it will carry
- Adequate or undersized, judged against whichever limit binds first

THE MATERIAL CHANGES THE ANSWER
- Galvanized, duct board or flexible duct, each with its own ASHRAE roughness
- Flex needs a full standard size more than metal at the same airflow. Size a flex
  run as if it were sheet metal and it always goes in over the friction rate it was
  designed for, by up to double

BUILT ON REAL PHYSICS
- Darcy-Weisbach with the Colebrook friction factor, solved on the spot. It is the
  method behind the ASHRAE friction chart and professional ductulators
- Standard air, with supply (0.10 in wg/100ft) and return (0.08) defaults built in,
  or set your own friction rate
- A friction rate you enter is yours. Switching between supply and return never
  overwrites it, because Manual D designs one system to one rate

Terms: https://ductulator.vovaluka.com/terms
Privacy: https://ductulator.vovaluka.com/privacy

## Pricing and in-app purchases

Base price: Free.

**Subscriptions**

| Subscription | Price | Period |
| --- | --- | --- |
| Ductulator Pro | $9.99 | per year |



## Version history (last 3 releases)

### 1.1.0 — 2026-09-01

Duct material now changes the answer. Galvanized, duct board and flexible duct each
carry their own ASHRAE roughness, and flex needs a full standard size more than metal
at the same airflow. Size a flex run as if it were metal and it always goes in over
its design friction rate, by up to double.

New Check tab for the duct that's already there: type in a round diameter or a width
and height and read back its velocity, its friction rate, and the airflow it will
actually carry, with a verdict against whichever limit binds first.

Also: a friction rate you type in now survives switching between supply and return.
Manual D designs a whole system to one rate, so the per-service defaults no longer
overwrite a number you worked out yourself.

### 1.0.1 — 2026-08-04

Fixes a crash when typing your own friction rate, keeps the Wheel and the Calculator on the same airflow, and stops the rating prompt from appearing before you've had a chance to use the app.

### 1.0 — 2026-07-15

No release notes.

## Apps similar to Duct Calculator

| App | Rating | Price | Category |
| --- | --- | --- | --- |
| [Allday HVAC Calc](https://appshunter.io/ios/app/allday-hvac-calc/id6446276144) | 5.0 (1) | Free | Utilities |
| [Fb2-to-ePub](https://appshunter.io/ios/app/fb2-to-epub/id541521102) | — | Free | Utilities |
| [Duct Calculator - DuctCalc](https://appshunter.io/ios/app/duct-calculator-ductcalc/id6757307937) | 4.6 (32) | Free | Utilities |
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| [Duct Calculator S&P](https://appshunter.io/ios/app/duct-calculator-s-and-p/id1096043356) | 5.0 (1) | Free | Utilities |

## More apps by Vladimir Lukashov

- [Candle & Soap Calculator](https://appshunter.io/ios/app/candle-and-soap-calculator/id6783697229)
- [Tee Time Alerts](https://appshunter.io/ios/app/tee-time-alerts/id6784973886)
- [Schengen Calculator & Tracker](https://appshunter.io/ios/app/schengen-calculator-and-tracker/id6786868571)
- [Daysworth: Daily Budget](https://appshunter.io/ios/app/daysworth-daily-budget/id6787101947)
- [HVAC Load Calc: Manual J](https://appshunter.io/ios/app/hvac-load-calc-manual-j/id6789243124)

All apps by Vladimir Lukashov: https://appshunter.io/developer/6783697231

## Related topics

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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 2026-09-02.*