# O vs Thread Calculator

The clearest difference is review sentiment: O at 83% against Thread Calculator's 33%. O also leads on ads (none vs shown) and update cadence (every 3 months vs every 18 months). Thread Calculator's advantage is rating (4.3 vs 3.8). On price, ratings volume, 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.

Thread Calculator holds the better App Store score, 4.3 against 3.8. Both are backed by a comparable volume of ratings — 5 and 13 respectively. Written reviews complicate that: 83% of O's written reviews are positive against 33% of Thread Calculator's, so the app with the better star average is not the one people write more warmly about.

O ships an update every 3 months, Thread Calculator every 18 months. The most recent releases landed on June 4, 2026 and September 9, 2026 respectively.

## The numbers

| Metric | O | Thread Calculator |
| --- | --- | --- |
| Price | Free | Free |
| Rating | [3.8 (5 ratings)](https://appshunter.io/ios/app/o-ring/id485346224/reviews) | **[4.3 (13 ratings)](https://appshunter.io/ios/app/thread-calculator/id1559560290/reviews)** |
| Number of ratings | 5 | **13** |
| Positive reviews | **83.3% of reviews** | 33.3% of reviews |
| In-app purchases | No | No |
| Ads | **No** | Yes |
| Update frequency | **Every 3 months** | Every 18 months |
| Monetization | **Free** | Ad-supported |
| Size | 26 MB | 25 MB |
| Requires iOS | **12.1** | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 12+ | 4+ |
| Developer | [Trelleborg Sealing Solutions](https://appshunter.io/developer/396863758) | [GSR Gustav Stursberg GmbH](https://appshunter.io/developer/1559560292) |

## What reviewers say

### O

[App page](https://appshunter.io/ios/app/o-ring/id485346224)

This app helps users calculate O-Ring dimensions and find compatible materials for their applications. It provides recommendations based on ISO standards and supports both metric and inch measurements.

**Highlights:** O-Ring housing calculation, O-Ring size recommendations by ISO standard, Quick search by national/international standards, O-Ring tolerance calculation, Metric and inch unit switching, Chemical compatibility check, Integration of Trelleborg Sealing Solutions Videos

**Features:** macOS Compatibility

**In-app purchases:** none


### Thread Calculator

[App page](https://appshunter.io/ios/app/thread-calculator/id1559560290)

This app provides a quick and easy way to calculate thread dimensions for various units, including tap hole sizes and bolt specifications. It helps metalworkers find precise measurements for internal and external threads without consulting tables.

**Highlights:** Thread cutting calculator for multiple units, Cold forming calculator, Thread repair calculator, Tap hole and bolt diameter calculation, Saves time compared to tables

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is O free?

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

### Is Thread Calculator free?

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

### Which has better reviews, O or Thread Calculator?

Thread Calculator is rated higher. O averages 3.8 out of 5 from 5 ratings, while Thread Calculator averages 4.3 from 13 ratings.

### Do O or Thread Calculator have ads?

Thread Calculator shows ads; O does not.

### Which is updated more often, O or Thread Calculator?

O ships an update every 3 months, and Thread Calculator every 18 months. Most recently, O was updated on June 4, 2026 and Thread Calculator on September 9, 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.*