# Propeller Calc vs Mariner Check

The clearest difference is rating: Mariner Check at 5.0 against Propeller Calc's 3.0. Propeller Calc's advantage is iOS requirement (17.0 vs 26.5). On price, ratings volume, ads and in-app purchases there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Mariner Check holds the better App Store score, 5.0 against 3.0. Both are backed by a comparable volume of ratings — 1 and 1 respectively.

## The numbers

| Metric | Propeller Calc | Mariner Check |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.0 (1 ratings)](https://appshunter.io/ios/app/propeller-calc/id478119478/reviews) | **[5.0 (1 ratings)](https://appshunter.io/ios/app/mariner-check/id6801565663/reviews)** |
| Number of ratings | 1 | 1 |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 21 months | — |
| Monetization | Free | Free |
| Size | 3 MB | 4 MB |
| Requires iOS | **17.0** | 26.5 |
| Devices | iPhone, iPad | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Frode Rørvik](https://appshunter.io/developer/478119481) | [KEVIN M GRAVES](https://appshunter.io/developer/1875176384) |

## What reviewers say

### Propeller Calc

[App page](https://appshunter.io/ios/app/propeller-calc/id478119478)

This utility calculates propeller performance metrics like pitch, gear ratio, RPM, slip, and speed. Input any four values, and the app computes the fifth, helping users understand the relationship between propeller design and boat performance.

**Highlights:** Calculate pitch, gear ratio, RPM, slip, and speed, Enter any four variables to find the fifth, Understand propeller slip and its impact, Supports iPhone and iPad, Free to use

**Features:** macOS Compatibility

**In-app purchases:** none


### Mariner Check

[App page](https://appshunter.io/ios/app/mariner-check/id6801565663)

Organize professional mariner credentials and track renewal dates. View status at a glance, set custom reminders, and manage multiple document types. Stay prepared for renewals with this convenient organizational tool.

**Highlights:** Organize credentials, Track renewal dates, Custom renewal windows, Expiration reminders, Home Screen widget, Offline access, Mask credential numbers

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

**In-app purchases:** none


## Frequently asked questions

### Is Propeller Calc free?

Propeller Calc is free to download, with no in-app purchases.

### Is Mariner Check free?

Mariner Check is free to download, with no in-app purchases.

### Which has better reviews, Propeller Calc or Mariner Check?

Mariner Check is rated higher. Propeller Calc averages 3.0 out of 5 from 1 ratings, while Mariner Check averages 5.0 from 1 ratings.

### Do Propeller Calc or Mariner Check have ads?

Neither Propeller Calc nor Mariner Check shows ads.

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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.*