# Free42 by Thomas Okken

7 Hacker News commenters recommended Free42 by Thomas Okken and 0 criticized it, November 2025 to November 2026. It was recommended in 5 of 13 months.

**Verdict:** A free emulator of the HP-42S RPN scientific calculator that runs on phones, favored by people who like RPN calculators.

## Why people recommend it

- Free and GPL licensed (2 comments): "a great choice is the Free42 project by Thomas Okken, which is a GPL-licensed project that is entirely compatible with the HP-42" ([source](https://news.ycombinator.com/item?id=48183539)) "Thomas Okken's free42 is a great, free HP42S emulator which runs on iOS." ([source](https://news.ycombinator.com/item?id=46870762))
- Faithful HP-42S emulation (2 comments): "a great choice is the Free42 project by Thomas Okken, which is a GPL-licensed project that is entirely compatible with the HP-42" ([source](https://news.ycombinator.com/item?id=48183539)) "Thomas Okken's free42 is a great, free HP42S emulator which runs on iOS." ([source](https://news.ycombinator.com/item?id=46870762))
- Used on phone daily (2 comments): "up to and including the Free42 on my phone today" ([source](https://news.ycombinator.com/item?id=48383194)) "If I don't have it in hand I use Free42" ([source](https://news.ycombinator.com/item?id=48378107))

## Alternatives hackers recommend

- [SpeedCrunch](https://hackerapproved.com/p/speedcrunch-1-1.md): 13 recommend
- [Qalculate](https://hackerapproved.com/p/qalculate.md): 9 recommend
- [iPhone Calculator app](https://hackerapproved.com/p/apple-calculator-app.md): 6 recommend
- [Math Notepad](https://hackerapproved.com/p/math-notepad.md): 6 recommend

## Cite as

Hacker Approved, "Free42 by Thomas Okken", https://hackerapproved.com/p/free42/ (counts from 1,795,640 Hacker News comments, November 2025 to November 2026).