CalcStak

Reverse Polish Calculator for iPhone

Built for people who think in stacks. No equals key, no parentheses — just clean RPN math, history, and a keyboard that gets out of your way.

Coming soon to the App Store.

Why RPN

If you've used an HP-12C, a Forth REPL, or any stack-based calculator, you already know: RPN is faster once your fingers know the moves. CalcStak puts that experience on your phone without the skeuomorphic clutter.

Features

• Stack display — see four levels at a glance, scroll deeper
• Full keyboard — numeric pad, operators, and stack manipulation (swap, drop, roll, LASTX)
• Configurable angle mode (degrees / radians), stack mode (unlimited or HP-classic four-deep), and ENTER behavior
• Storage registers (STO/RCL 0–9) for holding values across calculations
• History — every operation, scrollable; tap a row to push that past result onto the stack. Capped at the most recent 150 entries
• Optional Scientific pack (one-time in-app purchase): trig + inverses, log/ln, 10ˣ/eˣ, powers, roots, π and e
• Dark mode and a calm, monospace-forward design
• Offline-only. No tracking, no analytics, no network calls. Your math stays on your phone.

Not included (by design)

• No "infix mode." This is RPN. If that's not what you wanted, this isn't your app.
• No cloud sync. Yet.
• No ads, ever.

Privacy

CalcStak collects nothing. The app does not make network requests. Settings and history are stored on-device. See the full privacy policy.

Support

Questions, bug reports, feature requests: support@rosinbum.org. See the support page for the FAQ.