# ISO vs Ductulator

The clearest difference is update cadence: Ductulator at every 2 months against ISO's every 18 months. Ductulator also leads on chart position (#31 vs unranked). ISO's advantage is price ($0.99 vs $3.99) and iOS requirement (15.6 vs 18.6). On ads, in-app purchases and device support there is nothing between them.

ISO costs $0.99 and Ductulator $3.99 up front. Neither carries in-app purchases, so what you see is what you pay.

ISO ships an update every 18 months, Ductulator every 2 months. The most recent releases landed on September 28, 2026 and October 26, 2026 respectively.

## The numbers

| Metric | ISO | Ductulator |
| --- | --- | --- |
| Price | **$0.99** | $3.99 |
| Rating | — | **[4.7 (353 ratings)](https://appshunter.io/ios/app/ductulator-duct-sizing/id1474939475/reviews)** |
| Number of ratings | — | **353** |
| Positive reviews | — | 50.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 18 months | **Every 2 months** |
| Monetization | — | Free |
| Best chart rank | — | **#31** |
| Size | 1 MB | 1 MB |
| Requires iOS | **15.6** | 18.6 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 17+ | 4+ |
| Developer | [Bjarne Berge](https://appshunter.io/developer/1209858941) | [Wassim Murr](https://appshunter.io/developer/1474939474) |

## What reviewers say

### ISO

[App page](https://appshunter.io/ios/app/iso-5167/id1356345079)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none


### Ductulator

[App page](https://appshunter.io/ios/app/ductulator-duct-sizing/id1474939475)

**Currently charting:** #31 Top Paid · Productivity (US App Store)

Instantly calculate HVAC duct sizes based on airflow, friction rate, or velocity. This tool provides accurate duct dimensions in seconds without needing charts, supporting various duct types and units.

**Highlights:** Instant duct sizing, Friction rate or velocity calculation, Multiple valid duct dimensions, IP and SI units support, Detailed sizing mode, Rectangular, circular, and flexible ducts

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases:** none

**What reviewers like**

- 👍 Very helpful for duct sizing
- 👍 Easy to use in the field
- 👍 Saves time
- 👍 Seamless imperial/metric transitions
- 👍 Excellent tool for duct design

**What reviewers complain about**

- 👎 App should be free
- 👎 Functionality is pointless for some needs
- 👎 Doesn't help with traditional residential HVAC duct sizing
- 👎 App is a scam
- 👎 Decimal point doesn't work

**Reported bugs**

- Decimal point doesn't work on calculator
- New flex option isn't working properly
- Friction rate can't be changed in the latest version
- Skips duct sizes (e.g., 24-26)

**Requested features**

- Ability to pick duct size and see CFM
- Include flat oval ducts
- Option to select round or square duct
- Ability to enter duct size and get CFM
- Option for flex duct


## Frequently asked questions

### Is ISO free?

ISO costs $0.99, with no in-app purchases.

### Is Ductulator free?

Ductulator costs $3.99, with no in-app purchases.

### Do ISO or Ductulator have ads?

Neither ISO nor Ductulator shows ads.

### Which is updated more often, ISO or Ductulator?

ISO ships an update every 18 months, and Ductulator every 2 months. Most recently, ISO was updated on September 28, 2026 and Ductulator on October 26, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*