Free42 review
A free HP-42S-style simulator for programmable calculations across desktop and mobile.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
Free42 reimplements the HP-42S scientific programmable calculator and HP-82240 printer as software, for people who want an HP-42S-style calculator on desktop or mobile. It can run programs written for the HP-42S and supports user-written programs, making it relevant to users who want programmable calculations rather than a general equation-solving or graphing app. The project is open source under GPLv2 and has downloads for Windows, macOS, Linux, iOS, and Android.
Its feature set goes beyond basic real-number calculations: Free42 supports complex numbers and real and complex matrices. It provides decimal and binary floating-point versions, date and time functions, and configurable BASE operations. Users can import and export programs, copy and paste them, and save, share, or switch calculator states. Those capabilities make it a focused option for users who value an HP-42S workflow and reusable programs; they do not make it a broad equation-solving tool.
Free42 is free, with no paid tiers to weigh against those capabilities. Its cross-platform availability lets users keep the same calculator approach across desktop and mobile, while its email, community, and documentation channels provide support routes. The trade-off is its deliberate focus: it simulates the HP-42S rather than offering equation solving or graphing. Choose Free42 for programmable HP-42S-style calculations, complex arithmetic, and matrices; look elsewhere if equation solving or graphing is central to your work.
Free42 pros and cons
- Where it wins
- Runs HP-42S programs and simulates the HP-82240 printer
- Supports real and complex numbers, plus real and complex matrices
- Free, open source, and available on desktop and mobile
- Where it doesn't
- Focuses on HP-42S simulation rather than broad equation solving
- Does not provide equation solving
- Its programmable calculator approach may not suit users seeking graphing
Free42 fact sheet, pricing and score →
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