Screenshot of the free online Casio-style fx-991ES PLUS scientific calculator showing the definite integral ∫(X², 0, 3) = 9 Free online scientific calculator Open the Casio-style fx-991ES PLUS calculator 403 functions across 10 modes — calculus, matrices, complex numbers, statistics, base-N. No download, no sign-up. Open calculator →
Comparison

Best Casio fx-991ES PLUS Alternatives You Can Use in a Browser

Lost your calculator, on a different device, or just want to practise? Here's what a true online replacement needs to replicate — and how the options compare.

AppynoxUpdated 23 June 20267 min read

The Casio fx-991ES PLUS is one of the most popular exam calculators in the world, so "is there a Casio fx-991ES PLUS online?" is a common search. The honest answer: there is no official Casio browser edition for everyday use, but independent Casio-style alternatives (including Appynox) cover the modes for practice and homework.

On this page

  1. Why use one online
  2. What a true alternative must replicate
  3. The options
  4. How they compare
  5. An honest caveat
  6. FAQ

Why use one online

What a true alternative must replicate

A graphing tool isn't a substitute — emulation means matching the actual machine:

The options

Appynox (this site)

A single-page Casio-style fx-991ES PLUS calculator with the familiar keypad, natural display and main modes — free, independent, and offline-capable as a PWA. Built for practice in a browser tab.

Graphing tools (Desmos, GeoGebra)

Powerful and free, but a different paradigm — they don't match the Casio-style keypad or its base-N and exam-mode workflow. Great companions, not replacements. (See Desmos vs Google vs a full scientific calculator.)

Other browser calculators

Several exist; judge them by the checklist above — especially whether base-N, matrices and complex numbers actually work, not just the trig keys.

How they compare

NeedAppynoxDesmos / GeoGebra
Same keypad & modesYesNo
Natural textbook displayYesPartial
Base-N & bitwiseYesNo
GraphingNoYes
Free & offline (PWA)YesVaries

An honest caveat

Independent tool, not Casio hardware

Browser alternatives recreate familiar modes but aren't the physical device and aren't affiliated with Casio. Some advanced behaviours can differ, and online tools are not permitted in exams — use them for practice and checking. For everything Appynox can do, see the full documentation.

Frequently asked questions

Is there a Casio fx-991ES PLUS online?

No official Casio browser edition for everyday practice — but Casio-style tools recreate its modes and keypad. Appynox is a free independent option covering the main modes.

What should a good alternative replicate?

Natural display, the multi-mode engine, the SHIFT/ALPHA keypad, and angle-mode handling.

Are online calculators allowed in exams?

Generally no — use them for practice, homework and checking.

Use a Casio-style fx-991ES PLUS online

Familiar modes and keypad, free, in your browser — install Appynox for offline use.

Open the Appynox calculator →
Screenshot of the free online Casio-style fx-991ES PLUS scientific calculator showing the definite integral ∫(X², 0, 3) = 9 Free · No sign-up · Works offline Open the Scientific Calculator A Casio fx-991ES PLUS–style calculator in your browser — 403 functions: calculus, matrices, complex numbers, statistics, base-N & equation solving. Open Calculator →