Simple RPN

The RPN calculator for everyday use.
Not just for engineers or scientists — for anyone who wants to calculate efficiently, precisely and without distractions. From the grocery store to the construction site, from the office to the lab.
Built on Reverse Polish Notation — the method used by Hewlett-Packard engineers since the 1970s — it eliminates parentheses and lets the stack manage the order of operations for you. Once you try it, you won't go back.
— 4-LEVEL STACK — T, Z, Y and X registers always visible. ENTER, DROP, SWAP and R↓ to navigate the stack with precision. Full history with unlimited Undo and Redo.
— SCIENTIFIC FUNCTIONS — Full trigonometry (sin, cos, tan and inverses) in degrees or radians. Natural and base-10 logarithms, exponentials, powers, roots, π. Factorial, MOD, configurable rounding in steps of 1, ½ or ¼.
— PERCENTAGES AND STATISTICS — Percentage of total (%T), percentage change (Δ%), TAX calculation with three customisable tax rates and instant reverse. Configurable tip calculator. Statistics accumulator with mean, selective add and remove.
— MEMORY — Ten persistent registers (M1–M10) saved between sessions. Perfect for exchange rates, project constants or any reference value.
— INTERFACE — Four-row display always easy to read. Sans or Mono font. Thousands separator, 0 to 10 decimal places, DEG/RAD mode with visual indicator. History browsing with a swipe on the display.
— AD-FREE — No banners, no notifications, no subscriptions. One complete app, forever.
Full user manual with examples: https://stileottica.ch/app