# testo Smart vs Duct Calculator

The clearest difference is rating: Duct Calculator at 4.7 against testo Smart's 2.7. Duct Calculator also leads on iOS requirement (15.6 vs 18.0). testo Smart's advantage is update cadence (every 2 months vs every 10 months) and ratings volume (170 vs 3). On price, ads, in-app purchases and monetization model there is nothing between them.

Both are free to download. testo Smart sells 5 in-app purchases, starting at $6.99 per month and Duct Calculator sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

Duct Calculator holds the better App Store score, 4.7 against 2.7. That said, the two scores are not equally well evidenced: testo Smart has 170 ratings behind it against 3, so its average is the more settled of the two.

testo Smart ships an update every 2 months, Duct Calculator every 10 months. The most recent releases landed on October 25, 2026 and October 26, 2026 respectively.

## The numbers

| Metric | testo Smart | Duct Calculator |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [2.7 (170 ratings)](https://appshunter.io/ios/app/testo-smart/id1482139629/reviews) | **[4.7 (3 ratings)](https://appshunter.io/ios/app/duct-calculator-hvac-sizing/id6756908372/reviews)** |
| Number of ratings | **170** | 3 |
| Positive reviews | 16.3% of reviews | — |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | **Every 2 months** | Every 10 months |
| Monetization | Free with in-app purchases | Free with in-app purchases |
| Size | 195 MB | 44 MB |
| Requires iOS | 18.0 | **15.6** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Testo SE & Co. KGaA](https://appshunter.io/developer/966489178) | [Sachinbhai Surani](https://appshunter.io/developer/1838685550) |

## What reviewers say

### testo Smart

[App page](https://appshunter.io/ios/app/testo-smart/id1482139629)

This app supports measurements for refrigeration, HVAC, and heating systems. It also aids in food safety, frying oil quality, and indoor climate monitoring. Quickly interpret data, create digital reports with photos, and send them via email.

**Highlights:** All-in-one system measurements, Graphical display of measured values, Digital PDF/CSV measurement reports, Email report sharing, Leak test analysis, Automatic refrigerant charging, Indoor air quality monitoring

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

**In-app purchases (5)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Multi-site measurement | $6.99 | per month |
| Air balancing | $9.99 | per month |
| Multi-site measurement | $69.90 | per year |
| Air balancing | $99.90 | per year |
| Logging digital manifold | $44.99 | one-time |

**What reviewers like**

- 👍 Good app with some features
- 🚀 Great product
- 🚀 Useful app for measurements

**What reviewers complain about**

- 🐛 App won't connect
- 🐛 Connectivity issues
- 🐛 Unreliable connection
- 🐛 Forced updates
- 🐛 Laggy and unresponsive UI

**Reported bugs**

- App won't connect to devices
- Compatibility issues with newer iOS versions
- Frequent crashes and freezes
- Inability to save favorite refrigerants
- Measurement data not displaying properly

**Requested features**

- Add option to toggle Bluetooth discovery
- Improve Bluetooth range
- Add ability to customize colors and graphs
- Improve data export functionality
- Add option to name sensors


### Duct Calculator

[App page](https://appshunter.io/ios/app/duct-calculator-hvac-sizing/id6756908372)

This professional HVAC utility assists engineers and technicians with precise duct sizing and airflow calculations for ventilation systems. It simplifies essential calculations for both design and installation work, improving on-site efficiency.

**Highlights:** Calculate duct sizes using airflow (CFM) and velocity (FPM), Supports rectangular and round duct sizing in inches, Determine air flow rate in CFM, Calculate air velocity in FPM, Simple interface for fast on-site calculations

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Lifetime premium | $9.99 | one-time |


## Frequently asked questions

### Is testo Smart free?

testo Smart is free to download, with in-app purchases available.

### Is Duct Calculator free?

Duct Calculator is free to download, with in-app purchases available.

### Which has better reviews, testo Smart or Duct Calculator?

Duct Calculator is rated higher. testo Smart averages 2.7 out of 5 from 170 ratings, while Duct Calculator averages 4.7 from 3 ratings.

### Do testo Smart or Duct Calculator have ads?

Neither testo Smart nor Duct Calculator shows ads.

### Which is updated more often, testo Smart or Duct Calculator?

testo Smart ships an update every 2 months, and Duct Calculator every 10 months. Most recently, testo Smart was updated on October 25, 2026 and Duct Calculator 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.*