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kalker vs Plus42: catalog facts
kalker	Plus42
Free Free and open source under the MIT licence.	Free Desktop builds are free and open source under GPL-2.0; mobile store pricing is not stated.
Windows, macOS, Linux, Android, Web, Command line	Windows, macOS, Linux, Android, iOS
Natural math syntax with user-defined functions and variables Handles complex numbers, vectors and matrices	Faithful HP-42S behaviour with modern additions Plotting, units and TVM built in
Derivatives and integrals are numerical estimates Higher-order derivatives can be inaccurate	RPN workflow takes time to learn Aimed at HP calculator users rather than casual use
Downloadable app, Web application	Downloadable app
Open source	Open source
License: MIT	License: GPL-2.0
No account needed	No account needed
Works offline	Works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.