# Rule of Three - Calculator — Simple Rule of 3 calculator

> Simple calculator for direct and indirect proportion rule of three problems. (iPhone/iPad app by Tomas Parizek.)

- Source: https://appshunter.io/ios/app/rule-of-three-calculator/id1489858521 (this page in markdown: same URL + `.md`)
- Developer: [Tomas Parizek](https://appshunter.io/developer/1425394913)
- Category: Utilities, Education
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 13.0 · 5 MB
- Languages: American English, European Spanish, Slovak, Chinese (Simplified, China), Czech
- Released: 2019-12-04
- Data updated: 2026-08-23
- Monetization: free with in-app purchases
- User reviews in markdown: https://appshunter.io/ios/app/rule-of-three-calculator/id1489858521/reviews.md

## What is Rule of Three?

Simple calculator for the Rule of Three. Supports for both direct proportion and indirect proportion mode.

Accessibility should be an important part of every application. Rule of Three Calculator is tested and optimized for use via VoiceOver and other accessibility features.

If you have any issue with the app or you have a suggestion for an improvement, do not hesitate to contact me via email: rule_off_three@tomasparizek.com

## Key features

- Direct proportion calculations
- Indirect proportion calculations
- Accessibility optimized
- VoiceOver support

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Remove ads | $1.99 | one-time |


## Recent user reviews (1 of 1)

All indexed reviews: https://appshunter.io/ios/app/rule-of-three-calculator/id1489858521/reviews.md

### 5/5 — Great!

*2025-08-09*

Great app! I just wish the number pad would disappear when you’re not entering any values.

## Frequently asked questions about Rule of Three

### What is the Rule of Three calculator?

The Rule of Three calculator is a utility app designed to help users solve mathematical problems involving direct and indirect proportions. It offers a simple interface for these specific calculations.

### Does the Rule of Three calculator support both direct and indirect proportions?

Yes, the Rule of Three calculator supports both direct proportion and indirect proportion modes, allowing users to tackle a wider range of ratio-based problems.

### Is the Rule of Three calculator accessible?

Yes, the Rule of Three calculator is tested and optimized for use with accessibility features like VoiceOver. This ensures it is usable by individuals with visual impairments.

### What devices is the Rule of Three calculator available on?

The Rule of Three calculator is available for iPhone, iPad, and iPod touch devices. It was released on December 4, 2019, and last updated on September 17, 2020.

### What is the age rating for the Rule of Three calculator?

The Rule of Three calculator has an age rating of 4+, making it suitable for a wide range of users. It is a simple utility tool with no mature content.

### How often is the Rule of Three calculator updated?

The Rule of Three calculator was last updated on September 17, 2020, with version 1.1.3. While updates may not be frequent, the app is stable for its intended purpose.

### Can I contact the developer with issues or suggestions for the Rule of Three calculator?

Yes, you can contact the developer, Tomas Parizek, via email at rule_off_three@tomasparizek.com with any issues or suggestions for improvement.

### Does the Rule of Three calculator have ads?

No, the Rule of Three calculator does not contain advertisements. It is a free app with optional in-app purchases.

## Version history (last 5 releases)

### 1.1.3 — 2020-09-17

iOS 14 optimization

### 1.1.2 — 2020-06-22

Accessibility: VoiceOver optimization

### 1.1.1 — 2020-05-19

- New language support: Spanish and Chinese (simplified)

### 1.1.0 — 2019-12-18

- In-app payment for removing ads and supporting the development of the application
- New splash screen

### 1.0.2 — 2019-12-05

- Bugfixing

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| [Recipe Scaler & Rule of Three](https://appshunter.io/ios/app/recipe-scaler-and-rule-of-three/id1508332297) | — | Free | Utilities |
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## More apps by Tomas Parizek

- [My BatteryStatus](https://appshunter.io/ios/app/my-batterystatus/id1179495715)
- [SLibrary](https://appshunter.io/ios/app/slibrary/id1425394914)
- [Health Export CSV](https://appshunter.io/ios/app/health-export-csv/id1477944755)
- [EventBattle: Scavenger Hunt](https://appshunter.io/ios/app/eventbattle-scavenger-hunt/id1493449748)
- [WSS WebSocket Client](https://appshunter.io/ios/app/wss-websocket-client/id1505337953)

All apps by Tomas Parizek: https://appshunter.io/developer/1425394913

## Related topics

[rule of three calculator](https://appshunter.io/ios/topics/rule-of-three-calculator) · [Rule of Three](https://appshunter.io/ios/topics/rule-of-three) · [rule of three calculator pro](https://appshunter.io/ios/topics/rule-of-three-calculator-pro)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-23.*