# Propeller Calc vs MAR

The clearest difference is update cadence: MAR at every 3 months against Propeller Calc's every 21 months. MAR also leads on iOS requirement (15.6 vs 17.0). On price, ads, in-app purchases and device support there is nothing between them.

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

Propeller Calc ships an update every 21 months, MAR every 3 months. The most recent releases landed on September 26, 2026 and October 19, 2026 respectively.

## The numbers

| Metric | Propeller Calc | MAR |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.0 (1 ratings)](https://appshunter.io/ios/app/propeller-calc/id478119478/reviews)** | — |
| Number of ratings | **1** | — |
| Positive reviews | 100.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 21 months | **Every 3 months** |
| Monetization | Free | — |
| Size | 3 MB | 84 MB |
| Requires iOS | 17.0 | **15.6** |
| Devices | iPhone, iPad | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Frode Rørvik](https://appshunter.io/developer/478119481) | [Locmarine Telematics, LLC](https://appshunter.io/developer/1511630052) |

## 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


### MAR

[App page](https://appshunter.io/ios/app/mar-ai/id6478054835)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Propeller Calc free?

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

### Is MAR free?

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

### Do Propeller Calc or MAR have ads?

Neither Propeller Calc nor MAR shows ads.

### Which is updated more often, Propeller Calc or MAR?

Propeller Calc ships an update every 21 months, and MAR every 3 months. Most recently, Propeller Calc was updated on September 26, 2026 and MAR on October 19, 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.*