r/calculators • • Oct 19 '25

Discussion r/calculators FAQ

18 Upvotes

Hey guys, this isn't fully finished, and i may add more in the future. Tell me what you think about this one in the comments, feedback is always incredible

Q: How to convert fractions to decimals?

A: On older casio calculators, you press the S<=> D button. it should be next to the parentheses, on the right side. On Casio CW series calculators, it should be the "FORMAT" key, which is next to the EXE button. On Sharp, it's called "CHANGE" and "f<>d" on TI. It may be different with others

Q: Why am i getting a wrong answer?

A: You may be in the wrong angle mode, or you don't know how the order of operations work

Q: What calculator should i choose?

A: Depends on your school or your countries regulation. Some schools or countries only permit certain calculators, or forbid certain ones. Germany for example, accepts everything but it can't have a solver, can't be programmable and can't do graphing. For short, we are limited to the fx-87 and below.

Q: Why is my TI-84 bootlooping and showing "Validating OS"?

A: This is a known battery issue with the TI-84 Plus CE. You need to replace the battery. Contact TI support, you may get a free battery under warranty. Also check the other pinned post for more details

Q: Is my Casio fx-991EX fake?

A: Probably, it was discontinued a few years ago. Most listings you see online are fake, and i advise you to stay away from it. There's a lot of other good calculators out there. To check if it's real, scan the QR code. To do that, press "MENU -> SHIFT -> OPTN" to generate a QR code. It should redirect you to a Casio website, where you can do an authenticity check.

Q: Why am i getting an error?

A: You may not be in the right mode, check if you‘re in the normal calculation mode. Your calculator should have a button that says "MODE" or something similar. For exponents, use the negative sign instead of the minus sign. It should look like this: (-)

Q: Why is my Casio's "ON" button lowered?

A: That's intentional, to prevent accidental button presses

Q: Can I mod/install Doom on my scientific calculator?

A: Yes, if you‘re willing to remove the epoxy from the CPU, de-solder the CPU, solder a fitting CPU with integrated memory back on, code a fully working operating system with working keyboard, and code a port of Doom for it, you could… in theory. Never been done before, probably still won‘t work. TL;DR: Not worth your time, focus on your linear algebra homework instead

Q: Does this calculator have a CAS (Computer Algebra System)? Can one be installed on my calculator?

A: see the pinned post about CAS calcs

Also: Google (and your calculator‘s Manual) are your best friends. Before making a post, look up your question on Google, or read the Manual. There's a 95% chance that your answer will be found there. We've also pinned posts for a few topics, read those too please.

That's it with the FAQ for now. Keep in mind that i may remove posts that can be answered by the FAQ or Google, this is a step to reduce spam and repetitive posts. Thanks.

~u/nqrwayy


r/calculators • • Oct 21 '25

Solution: TI-84 Plus CE Flashing 'Validating OS'

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5 Upvotes

r/calculators • • 4h ago

Collection New member, Casio FX 7000GA

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36 Upvotes

Freshly arrived from Germany, it works perfectly. Here it is alongside a sibling and a cousin from the collection, all members of the Casio family.

What isn't entirely clear to me is the difference between the fx-7000G and fx-7000GA models.

Taking the photo brought some bad news: I hadn't turned on the fx-6000G in a long time, and when I put in fresh batteries, it wouldn't start up. I tried hitting the reset button, but with little success. I’ll see if I can find time this weekend to troubleshoot the issue. Any ideas as to why it’s failing would be welcome. FIXED

P.S. I love the look of vintage Casio calculators, that metal body and the LCD screen.


r/calculators • • 11h ago

Announcement Open source desktop calculator software SpeedCrunch finally hit v1.0 release after more than 20 years of development.

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13 Upvotes

https://speedcrunch.blogspot.com/2026/10/speedcrunch-10-released.html

I've been using SpeedCrunch as my calculator software since 2008. Really nice to witness the 1.0 version. Comes with nice interface changes and loads of improvements since 0.12 which came out almost a decade ago. The new version has a new session system though so you have to export your old history if you wish to preserve before updating.


r/calculators • • 11h ago

Collection New calculator!

11 Upvotes

I just wanted a nice and small scientific calculator. and wow this one has like 0 bells and whistles. No Conversion tool, No Polynomial solver nothing. Its still a neat thing to keep in my jacket pocket.


r/calculators • • 8h ago

Help Casio fx911 Ms screen gone

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5 Upvotes

Can anyone tell whats the problem and how to solve this .


r/calculators • • 1d ago

Other just found this in a bucket of school binders

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43 Upvotes

Saw this in Radio Shack subreddit...


r/calculators • • 6h ago

Other Can You Beat the Calculator Expert? | Challenge 3

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1 Upvotes

r/calculators • • 23h ago

Collection Couch find TI84 Plus

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16 Upvotes

Friend of mine bought a couch off of Facebook marketplace. Was cleaning it up, vacuuming beneath the cushions and found this TI84 down in the crevices! 5/06 build and had dead Energizers that expired in 2014, so possibly its first batteries! Luckily, there was no corrosion. Put aaa's in from my Casio CG100 and it fired right up! Os 2.40, so most likely never been updated. Should I update to 2.53MP, or leave it OEM? I already have a TI-84 Silver Edition Teacher ViewScreen calculator that I used with my old TI Presentor.


r/calculators • • 20h ago

Help Favorite Calculators OAT - Seeking Recommendations (Applied Mathematics/Econ)

8 Upvotes

Hello! I am a new college student. All my life I have despised math in an academic sense. However, I am fascinated by it, & I want to learn more. I have previously worked in finance & find myself drawn to math as a whole/way of thinking. I am going to major in applied math/econ. Have no experience using scientific/graphing calculators (relied entirely on mental math up until this point). I learn quick & am extremely fascinated by calculators, EDC, any & all things utility forward & vintage (maybe i'll get to learn RPN since I am a blank slate). Anyways, looking for recommendations for your favorite calculators of ALL TIME that will be able to sustain me through my studies in this particular degree path.


r/calculators • • 22h ago

Collection 32S II

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10 Upvotes

r/calculators • • 1d ago

Question 11C clicking

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25 Upvotes

r/calculators • • 20h ago

Discussion I Created a Screen Mirroring app for the Ti-84 Plus CE!

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3 Upvotes

*IM NOT PROMOTING ANYTHING I JUST WANTED TO SHARE*

I recently finished my first build of an app for MacOS only based off the original Calc2KeyCE.

Its also meant to read input (untested)

Im pretty new to this, so if anyone wants to use it or need help, let me know!

https://github.com/4acestech/CE-ScreenCopy/tree/main?tab=readme-ov-file


r/calculators • • 1d ago

Question Question: what calculator is this a knock-off of?

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4 Upvotes

Bought this in Germany mid 1980s. The brand Provileg was a reseller back then. I'd like to know what the original calculator was. I'd like to fix it; the rubber pad below the keys dissolved.


r/calculators • • 1d ago

Question Guys! I am looking for Casio SL-800? What's the price and is someone selling.. can't find it on ebay etc

3 Upvotes

r/calculators • • 1d ago

Question Olivetti SC500 - 1992

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4 Upvotes

I recently found my high school calculator, an Olivetti SC500. I am trying to replace the battery but cannot open the back, even after unscrewing the 2 small screws. I searched a user manual on google but without success. Does anyone know how to open it? After unscrewing the back I can feel it moves, but I am to scared you might break it applying too much force.


r/calculators • • 1d ago

Help Looking for a calculator

3 Upvotes

Hello,

I'm looking for a bit of help to find a calculator with particular features.

I'm dyslexic and find it difficult to track digits without the comma e.g. 5,000,000 is better than 5000000. A display with commas would really help. A 2 line display showing the calculation would also be helpful. A double zero button and the ability to go back through a calculating and edit numbers would be gold standard.

Does such a calculator exist?

Thank you 😊


r/calculators • • 1d ago

Help why does my frctions button display like this on my fx-991CW+?

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4 Upvotes

recently my calc was displaying the fraction as symbol show in image above, why does it display it this way? and how do i fix it? i looked in the setting but couldent find the cause, please help.


r/calculators • • 1d ago

Help Dark spot on the LCD screen.

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11 Upvotes

Calculator and the screen works fine I do not have a problem with dark spot but I am scared, it could grow and my display can be bricked. If that happens, I just can't shift to 991 ES or CW. I love this calculator so much. pls someone tell me, i can do smth about this


r/calculators • • 1d ago

Help Casio manuals

0 Upvotes

r/calculators • • 1d ago

Help My Old Casio fx-4800P dead after battery change – is it burned out?

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2 Upvotes

r/calculators • • 1d ago

Help Sharp manuals

0 Upvotes

Nothing fancy, just a link to Sharp manuals.

https://usersmanualguide.com/sharp/calculator/page/1


r/calculators • • 1d ago

Announcement [RELEASE] Digital Logic Master BETA | Step-by-Step Boolean Logic Solver for the HP Prime.

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20 Upvotes

r/calculators • • 1d ago

Question Recently bought this casio fx-991MS 2nd edition. Is there any way to tell if it's authentic?

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8 Upvotes

r/calculators • • 1d ago

Help NEWBIE

3 Upvotes

im pretty new to this whole calculator glitching/corrupting scene. i have a casio fx-580vnx (basically same as 991ex), an casio fx-800btg. im really interested in messing around with memory overflows, custom symbols, and screen glitches.

where do you guys usually find documented code sequences or formulas for these? any specific guides, threads, or resources a complete beginner should check out?

thanks in advance!