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: not a free one. Casio runs ClassPad.net, where ClassPad Math is free but the ClassWiz emulator is paid, and none of it is an fx-991ES PLUS. Casio's own free online calculator service, keisan.casio.com, closed on 20 September 2023. So independent Casio-style alternatives, including WideMath, are what is left for practice and homework.
On this page
Why use one online
- You own the physical unit but it's not with you.
- You're working on a laptop or phone and want the same workflow.
- You're learning the calculator's key sequences before an exam.
- You want to check homework answers quickly and for free.
What a true alternative must replicate
A graphing tool isn't a substitute — emulation means matching the actual machine:
- Exact results, so √8 stays 2√2 and sin(180) returns 0 rather than 1.22e-16.
- The multi-mode engine — COMP, CMPLX, STAT, BASE-N, MATRIX, VECTOR, TABLE and EQN.
- SHIFT / ALPHA layered keypad so the key presses match.
- Angle modes (Deg / Rad / Grad) and the same function set.
The options
WideMath (this site)
A single-page Casio-style fx-991ES PLUS calculator with the familiar keypad, exact-result arithmetic and the 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
| Need | WideMath | Desmos / GeoGebra |
|---|---|---|
| Same keypad & modes | Yes | No |
| Exact results (√8 → 2√2) | Yes | Partial |
| Base-N & bitwise | Yes | No |
| Graphing | No | Yes |
| Free & offline (PWA) | Yes | Varies |
An honest caveat
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 WideMath 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. WideMath is a free independent option covering the main modes.
What should a good alternative replicate?
Exact results rather than rounded decimals, 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 WideMath for offline use.
Evaluate log(2,8) on the calculator →