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 browser calculators, including WideMath's free online scientific calculator, 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 online scientific calculator with a familiar handheld 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 a handheld 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 free Casio browser edition for everyday practice, but independent browser calculators follow the same modes and keypad workflow. 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 free scientific calculator online
Familiar modes and keypad, free, in your browser. Install WideMath for offline use.
Evaluate log(2,8) on the calculator →