# HydroCalc Plus vs CalcKey

The clearest difference is review sentiment: HydroCalc Plus at 100% against CalcKey's 0%. HydroCalc Plus also leads on rating (5.0 vs 3.8). CalcKey's advantage is price (Free vs $6.99) and ratings volume (8 vs 1). On update cadence, ads, in-app purchases and device support there is nothing between them.

CalcKey is free to download; HydroCalc Plus costs $6.99 up front. HydroCalc Plus sells 4 one-off in-app purchases and CalcKey sells 2 in-app purchases, starting at $3.99 per month. Whichever you choose, the download price is not the number that matters.

HydroCalc Plus holds the better App Store score, 5.0 against 3.8. That said, the two scores are not equally well evidenced: CalcKey has 8 ratings behind it against 1, so its average is the more settled of the two. Written reviews point the same way: 100% of HydroCalc Plus's written reviews are positive against 0% of CalcKey's.

Both ship on a similar rhythm, roughly every 3 weeks. The most recent releases landed on October 21, 2026 and October 13, 2026 respectively.

## The numbers

| Metric | HydroCalc Plus | CalcKey |
| --- | --- | --- |
| Price | $6.99 | **Free** |
| Rating | **[5.0 (1 ratings)](https://appshunter.io/ios/app/hydrocalc-plus/id578807688/reviews)** | [3.8 (8 ratings)](https://appshunter.io/ios/app/calckey-calculator-keyboard/id6748647909/reviews) |
| Number of ratings | 1 | **8** |
| Positive reviews | **100.0% of reviews** | 0.0% of reviews |
| In-app purchases | Yes | Yes |
| Ads | No | No |
| Update frequency | Every 3 weeks | Every 3 weeks |
| Monetization | Paid | **Free with in-app purchases** |
| Size | 34 MB | 14 MB |
| Requires iOS | 15.1 | **15** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Transparent Blue Water LLC](https://appshunter.io/developer/1847968351) | [Right Tracks IT Limited](https://appshunter.io/developer/1803615116) |

## What reviewers say

### HydroCalc Plus

[App page](https://appshunter.io/ios/app/hydrocalc-plus/id578807688)

A professional tool for hydraulic engineers to calculate pressure losses in piping systems. It supports US and SI units, offers an extensive pipe material and fittings database, and includes inverse calculations for design optimization.

**Highlights:** Friction head loss calculation (Hazen-Williams), US and SI unit support, Extensive pipe material library, Fittings and valves database, Inverse calculation mode, Real-time results (velocity, losses)

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

**In-app purchases (4)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Pump Power Calculator | $1.99 | one-time |
| System Curve Generator | $1.99 | one-time |
| Pipe Database | $1.99 | one-time |
| Industrial Fluids Pack | $2.99 | one-time |


### CalcKey

[App page](https://appshunter.io/ios/app/calckey-calculator-keyboard/id6748647909)

Perform calculations directly within any app using a smart keyboard extension. Get instant results for basic and scientific equations, with a history of your calculations. Enjoy a seamless typing experience and smart formatting.

**Highlights:** Keyboard calculator extension, Real-time results, Basic & scientific calculators, Calculation history, Smart formatting, Standalone app option

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

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| CalcKey Pro Monthly | $3.99 | per month |
| One time purchase | $19.99 | one-time |


## Frequently asked questions

### Is HydroCalc Plus free?

HydroCalc Plus costs $6.99, and also offers in-app purchases.

### Is CalcKey free?

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

### Which has better reviews, HydroCalc Plus or CalcKey?

HydroCalc Plus is rated higher. HydroCalc Plus averages 5.0 out of 5 from 1 ratings, while CalcKey averages 3.8 from 8 ratings.

### Do HydroCalc Plus or CalcKey have ads?

Neither HydroCalc Plus nor CalcKey shows ads.

### Which is updated more often, HydroCalc Plus or CalcKey?

HydroCalc Plus ships an update every 3 weeks, and CalcKey every 3 weeks. Most recently, HydroCalc Plus was updated on October 21, 2026 and CalcKey on October 13, 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.*