# DuctChecker vs ISO

The clearest difference is price: ISO at $0.99 against DuctChecker's $6.99. DuctChecker's advantage is update cadence (every 4 months vs every 18 months). On ads, in-app purchases, device support and iOS requirement there is nothing between them.

DuctChecker costs $6.99 and ISO $0.99 up front. Neither carries in-app purchases, so what you see is what you pay.

DuctChecker ships an update every 4 months, ISO every 18 months. The most recent releases landed on September 7, 2026 and July 4, 2026 respectively.

## The numbers

| Metric | DuctChecker | ISO |
| --- | --- | --- |
| Price | $6.99 | **$0.99** |
| Positive reviews | 0.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 4 months** | Every 18 months |
| Monetization | Paid | — |
| Size | 23 MB | 1 MB |
| Requires iOS | **15.0** | 15.6 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 17+ |
| Developer | [AIR DESIGN, INC.](https://appshunter.io/developer/923430781) | [Bjarne Berge](https://appshunter.io/developer/1209858941) |

## What reviewers say

### DuctChecker

[App page](https://appshunter.io/ios/app/ductchecker/id933593987)

Easily calculate duct dimensions using various engineering methods like constant pressure, static pressure regain, total pressure, and velocity. This tool simplifies complex duct design calculations, typically found in flow diagrams or slide rules.

**Highlights:** Constant pressure method calculation, Static pressure regain method, Total pressure method, Velocity method, Duct dimension determination, Simplified duct design

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

**In-app purchases:** none


### ISO

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

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is DuctChecker free?

DuctChecker costs $6.99, with no in-app purchases.

### Is ISO free?

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

### Do DuctChecker or ISO have ads?

Neither DuctChecker nor ISO shows ads.

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

DuctChecker ships an update every 4 months, and ISO every 18 months. Most recently, DuctChecker was updated on September 7, 2026 and ISO on July 4, 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.*