# GravLens3 vs Zetamac Arithmetic Practice

The clearest difference is rating: Zetamac Arithmetic Practice at 4.7 against GravLens3's 3.7. Zetamac Arithmetic Practice also leads on update cadence (daily vs every 17 months) and ratings volume (19 vs 6). GravLens3's advantage is iOS requirement (6.1 vs 17.5). On price, review sentiment, 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.

Zetamac Arithmetic Practice holds the better App Store score, 4.7 against 3.7. Both are backed by a comparable volume of ratings — 6 and 19 respectively. Written reviews point the same way: 80% of GravLens3's written reviews are positive against 83% of Zetamac Arithmetic Practice's.

GravLens3 ships an update every 17 months, Zetamac Arithmetic Practice daily. The most recent releases landed on October 23, 2026 and October 30, 2026 respectively.

## The numbers

| Metric | GravLens3 | Zetamac Arithmetic Practice |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.7 (6 ratings)](https://appshunter.io/ios/app/gravlens3/id318275930/reviews) | **[4.7 (19 ratings)](https://appshunter.io/ios/app/zetamac-arithmetic-practice/id6737153617/reviews)** |
| Number of ratings | 6 | **19** |
| Positive reviews | 80.0% of reviews | **83.3% of reviews** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 17 months | **Daily** |
| Monetization | Free | Free |
| Size | 4 MB | 1 MB |
| Requires iOS | **6.1** | 17.5 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [Eli Rykoff](https://appshunter.io/developer/318275933) | [Joseph Ma](https://appshunter.io/developer/1774979062) |

## What reviewers say

### GravLens3

[App page](https://appshunter.io/ios/app/gravlens3/id318275930)

Simulate the effects of gravitational lensing on your iPhone or iPad. Adjust lens parameters and apply distortions to your photos or live camera feed. Share your creations or project them for educational purposes.

**Highlights:** Simulate Hubble Space Telescope images, Adjust lens size and ellipticity, Distort photos from library or camera, Live real-time lensing view, AirPlay and external monitor support, Save and share distorted images

**Features:** macOS Compatibility

**In-app purchases:** none


### Zetamac Arithmetic Practice

[App page](https://appshunter.io/ios/app/zetamac-arithmetic-practice/id6737153617)

This app offers mental math practice tailored for quantitative finance professionals. It focuses on improving calculation speed and accuracy for complex numerical problems.

**Highlights:** Mental math practice, Quantitative finance focus, Calculation speed improvement, Accuracy enhancement, Numerical problem solving

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

**In-app purchases:** none


## Frequently asked questions

### Is GravLens3 free?

GravLens3 is free to download, with no in-app purchases.

### Is Zetamac Arithmetic Practice free?

Zetamac Arithmetic Practice is free to download, with no in-app purchases.

### Which has better reviews, GravLens3 or Zetamac Arithmetic Practice?

Zetamac Arithmetic Practice is rated higher. GravLens3 averages 3.7 out of 5 from 6 ratings, while Zetamac Arithmetic Practice averages 4.7 from 19 ratings.

### Do GravLens3 or Zetamac Arithmetic Practice have ads?

Neither GravLens3 nor Zetamac Arithmetic Practice shows ads.

### Which is updated more often, GravLens3 or Zetamac Arithmetic Practice?

GravLens3 ships an update every 17 months, and Zetamac Arithmetic Practice daily. Most recently, GravLens3 was updated on October 23, 2026 and Zetamac Arithmetic Practice on October 30, 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.*