{"slug": "free42", "name": "Free42", "category": "other", "category_name": "Other software", "description": "", "recommenders": 5, "commenters": 6, "warners": 0, "score": 4.657, "rising": -1.64, "first": "2026-02-01", "latest": "2026-06-03", "why": "Thomas Okken's free42 is a great, free HP42S emulator which runs on iOS.", "why_is_quote": true, "has_verdict": false, "sentiment": {"recommend": 6, "neutral": 1, "compare": 0, "warn": 0}, "spark": [0, 0, 0, 3, 0, 0, 2, 1, 0, 0, 0, 0], "listed": true, "loved": [], "caveat": "", "short_quote": "Thomas Okken's free42 is a great, free HP42S emulator which runs on iOS.", "kind": "", "icon": true, "domain": "thomasokken.com", "github_repo": null, "official_url": "https://thomasokken.com/free42/", "pricing": "", "aliases": ["Free42"], "verdict": null, "praise": [{"label": "", "summary": "", "quotes": [{"id": 774049712, "item_id": 48378107, "url": "https://news.ycombinator.com/item?id=48378107", "by": "downut", "date": "2026-06-02", "stance": "recommend", "quote": "If I don't have it in hand I use Free42.", "excerpt": "My wife and I were mid '80s chemical engineers. She liked her 15c, but I went on afterward into fundamental numerical analysis and was extremely happy with my 32S. I recently asked qwen3.6:35b|qwen3.6:27b|gemma4:31b (can't remember which one) all about the current state of replacement LR44 batteries for an \"HP 32S Scientific Calculator\". It was fucking adamant, aggressively so, that the calculator required 1 battery.", "context": "Mid-1980s chemical engineer, later numerical analyst", "use_case": "Calculator app substitute", "switched_from": "", "story": "HP re-releases classic computer science calculator: The HP-16C"}, {"id": 770936624, "item_id": 48183539, "url": "https://news.ycombinator.com/item?id=48183539", "by": "seanhunter", "date": "2026-05-18", "stance": "recommend", "quote": "a great choice is the Free42 project by Thomas Okken", "excerpt": "If you want a serious OSS calculator, a great choice is the Free42 project by Thomas Okken, which is a GPL-licensed project that is entirely compatible with the HP-42. https://thomasokken.com/free42/ Not really a graphing calculator (although you can plot a bit) but is a proper old-school rpn scientific calculator with programming, numerical integration and solver, amazing complex number support etc, and has stood th", "context": "", "use_case": "Scientific RPN calculator", "switched_from": "", "story": "Graphing Scientific Calculator Based on the ESP32"}, {"id": 767696144, "item_id": 47981009, "url": "https://news.ycombinator.com/item?id=47981009", "by": "drivers99", "date": "2026-05-01", "stance": "recommend", "quote": "It's great if you like RPN calculators", "excerpt": "Similarly, I still have my HP-42s but I usually use Free42[0] on my phone and tablet. They also have it for desktops. It's great if you like RPN calculators. Or if anyone wants to learn about them, you can use that program and follow along with the original manual(s)[1]. It's nice to be able to handle the order of operations without parentheses. [0] https://thomasokken.com/free42/ I should send them a donation. [1] h", "context": "", "use_case": "HP-42S calculator emulation", "switched_from": "", "story": "Ti-84 Evo"}, {"id": 749932193, "item_id": 46870762, "url": "https://news.ycombinator.com/item?id=46870762", "by": "seanhunter", "date": "2026-02-03", "stance": "recommend", "quote": "Thomas Okken's free42 is a great, free HP42S emulator which runs on iOS.", "excerpt": "Me too. Love my DM42. I also have an HP35s and two HP12Cs still on the batteries they were rocking over 10 years ago when I used them daily in my finance days. To answer the op's question, any RPN calculator is wildly better than the default calculators on things like iOS once you take the time to learn to use it[1]. If you want a good calculator app, Thomas Okken's free42 is a great, free HP42S emulator which runs o", "context": "", "use_case": "HP42S calculator emulator", "switched_from": "", "story": "Ask HN: Do you still physical calculators?"}, {"id": 749645393, "item_id": 46852837, "url": "https://news.ycombinator.com/item?id=46852837", "by": "watersb", "date": "2026-02-01", "stance": "recommend", "quote": "My other favorite calculator is free42", "excerpt": "PCalc -- because it runs on every Apple platform since the Mac Classic: https://pcalc.com/mac/thirty.html My other favorite calculator is free42, or its larger display version plus42 https://thomasokken.com/plus42/ For a CAS tool on a pocket mobile device, I haven't found anything better than MathStudio (formerly SpaceTime): https://mathstud.io You can run that in your web browser, but they maintain a mobile app vers", "context": "", "use_case": "", "switched_from": "", "story": "My thousand dollar iPhone can't do math"}]}], "caveats": [], "who": [{"by": "downut", "context": "Mid-1980s chemical engineer, later numerical analyst", "url": "https://news.ycombinator.com/item?id=48378107", "date": "2026-06-02"}], "tags": [], "use_cases": ["phone calculator", "calculator app substitute", "scientific rpn calculator", "hp-42s calculator emulation", "hp42s calculator emulator", "calculator app on all devices"], "compared": [], "makers": [], "threads": [{"url": "https://news.ycombinator.com/item?id=48374685", "title": "HP re-releases classic computer science calculator: The HP-16C", "mentions": 2}, {"url": "https://news.ycombinator.com/item?id=46834977", "title": "Ask HN: Do you still physical calculators?", "mentions": 2}, {"url": "https://news.ycombinator.com/item?id=48148351", "title": "Graphing Scientific Calculator Based on the ESP32", "mentions": 1}, {"url": "https://news.ycombinator.com/item?id=47979583", "title": "Ti-84 Evo", "mentions": 1}, {"url": "https://news.ycombinator.com/item?id=46849258", "title": "My thousand dollar iPhone can't do math", "mentions": 1}], "sentiment_by_month": {"2025-11": {}, "2025-12": {}, "2026-01": {}, "2026-02": {"recommend": 3}, "2026-03": {}, "2026-04": {}, "2026-05": {"recommend": 2}, "2026-06": {"recommend": 1, "neutral": 1}, "2026-07": {}, "2026-08": {}, "2026-09": {}, "2026-10": {}}, "quotes": [{"id": 774131104, "item_id": 48383194, "url": "https://news.ycombinator.com/item?id=48383194", "by": "Tor3", "date": "2026-06-03", "stance": "neutral", "quote": "up to and including the Free42 on my phone today", "excerpt": "When I started studying electronics in 1975 I didn't have a calculator, they were very expensive. Then rumours started about an upcoming low-cost Texas Instruments calculator, and IIRC early 1976 I could buy one - the TI-30. As did many of my classmates. The next year or two I used that one, and other similar calculators which entered the marked. Then one day a guy some two classes above me handed me a HP calculator ", "context": "", "use_case": "Phone calculator", "switched_from": "", "story": "HP re-releases classic computer science calculator: The HP-16C"}, {"id": 774049712, "item_id": 48378107, "url": "https://news.ycombinator.com/item?id=48378107", "by": "downut", "date": "2026-06-02", "stance": "recommend", "quote": "If I don't have it in hand I use Free42.", "excerpt": "My wife and I were mid '80s chemical engineers. She liked her 15c, but I went on afterward into fundamental numerical analysis and was extremely happy with my 32S. I recently asked qwen3.6:35b|qwen3.6:27b|gemma4:31b (can't remember which one) all about the current state of replacement LR44 batteries for an \"HP 32S Scientific Calculator\". It was fucking adamant, aggressively so, that the calculator required 1 battery.", "context": "Mid-1980s chemical engineer, later numerical analyst", "use_case": "Calculator app substitute", "switched_from": "", "story": "HP re-releases classic computer science calculator: The HP-16C"}, {"id": 770936624, "item_id": 48183539, "url": "https://news.ycombinator.com/item?id=48183539", "by": "seanhunter", "date": "2026-05-18", "stance": "recommend", "quote": "a great choice is the Free42 project by Thomas Okken", "excerpt": "If you want a serious OSS calculator, a great choice is the Free42 project by Thomas Okken, which is a GPL-licensed project that is entirely compatible with the HP-42. https://thomasokken.com/free42/ Not really a graphing calculator (although you can plot a bit) but is a proper old-school rpn scientific calculator with programming, numerical integration and solver, amazing complex number support etc, and has stood th", "context": "", "use_case": "Scientific RPN calculator", "switched_from": "", "story": "Graphing Scientific Calculator Based on the ESP32"}, {"id": 767696144, "item_id": 47981009, "url": "https://news.ycombinator.com/item?id=47981009", "by": "drivers99", "date": "2026-05-01", "stance": "recommend", "quote": "It's great if you like RPN calculators", "excerpt": "Similarly, I still have my HP-42s but I usually use Free42[0] on my phone and tablet. They also have it for desktops. It's great if you like RPN calculators. Or if anyone wants to learn about them, you can use that program and follow along with the original manual(s)[1]. It's nice to be able to handle the order of operations without parentheses. [0] https://thomasokken.com/free42/ I should send them a donation. [1] h", "context": "", "use_case": "HP-42S calculator emulation", "switched_from": "", "story": "Ti-84 Evo"}, {"id": 749932193, "item_id": 46870762, "url": "https://news.ycombinator.com/item?id=46870762", "by": "seanhunter", "date": "2026-02-03", "stance": "recommend", "quote": "Thomas Okken's free42 is a great, free HP42S emulator which runs on iOS.", "excerpt": "Me too. Love my DM42. I also have an HP35s and two HP12Cs still on the batteries they were rocking over 10 years ago when I used them daily in my finance days. To answer the op's question, any RPN calculator is wildly better than the default calculators on things like iOS once you take the time to learn to use it[1]. If you want a good calculator app, Thomas Okken's free42 is a great, free HP42S emulator which runs o", "context": "", "use_case": "HP42S calculator emulator", "switched_from": "", "story": "Ask HN: Do you still physical calculators?"}, {"id": 749645393, "item_id": 46852837, "url": "https://news.ycombinator.com/item?id=46852837", "by": "watersb", "date": "2026-02-01", "stance": "recommend", "quote": "My other favorite calculator is free42", "excerpt": "PCalc -- because it runs on every Apple platform since the Mac Classic: https://pcalc.com/mac/thirty.html My other favorite calculator is free42, or its larger display version plus42 https://thomasokken.com/plus42/ For a CAS tool on a pocket mobile device, I haven't found anything better than MathStudio (formerly SpaceTime): https://mathstud.io You can run that in your web browser, but they maintain a mobile app vers", "context": "", "use_case": "", "switched_from": "", "story": "My thousand dollar iPhone can't do math"}, {"id": 749516560, "item_id": 46844785, "url": "https://news.ycombinator.com/item?id=46844785", "by": "dubbie99", "date": "2026-02-01", "stance": "recommend", "quote": "", "excerpt": "I have one on my desk at work. I use it 2-3 times a week for quickly calculating things. It gives me a good feeling every time I use it.", "context": "", "use_case": "Calculator app on all devices", "switched_from": "", "story": "Ask HN: Do you still physical calculators?"}]}