r/calculators • u/nqrwayy • Oct 19 '25
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.
r/calculators • u/Edlegoboy • 2h ago
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I have just got this calculator and this is my first time using the graphing function.
WTF DO I DO?!?
r/calculators • u/FunRip7944 • 18m ago
My calculator started displaying these settings when i turn it on. Is there a way to reset it?
r/calculators • u/Ok-Sorbet-1968 • 7h ago
Dear all, hope this is the right place to ask.
I'm looking for a calculator that has LCM (lowest common multiple) for my son.
I tried the Casio FX-991 CW on Amazon (called the 2024 edition) but even if it advertised as having LMC, it's not there. I have read here on Reddit that it might depend on regional versions (I'm in Italy). So I will send it back.
Anyway, could anyone suggest a calculator that has LCM, possibily one that has no "regional versions" or different names depending on the country?
Thanks in advance :)
r/calculators • u/broken_console30 • 9h ago
r/calculators • u/BadOk3617 • 21h ago
Nice little calculator. Notice how the "5" has most of its segment out. A bit of battery damage, but not too terrible.
r/calculators • u/qqqqqrqqqq • 9h ago
pls ignore the domain as i got this cuz its free, pls recommend this to ur frineds and others asw, i made this as i didnt found any app that is same as real calculator so yeh give it a try
r/calculators • u/Reasonable_Quail1986 • 11h ago
Is Casio fx-350es Plus 2nd Edition allowed for PRC Board Exams? Confused lang since nakalagay kase sya sa list but for 2nd edition not sure.
r/calculators • u/CamelKing4253 • 14h ago
I just got the TI-84 Evo-T and wanna know what games you can download on it(bcs it's only tetris, pong,... and that's kinda boring bcs the other calculators have geometry daaaashhh...)
r/calculators • u/PopCalc-Calculator • 5h ago
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r/calculators • u/conrat4567 • 1d ago
Im not a calculator person, but I found it in a bin at a boot fair with other electronics that were deemed "junk". I bought it for a pound. I think its original case as well.
I fell in love with the display
r/calculators • u/ghost_BM • 1d ago
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It still calculates things properly.
I tried removing the battery and putting it back in
I tried the reset button
I opened up the calculator and found no visible damage (although im not an expert at figuring out what damaged stuff)
r/calculators • u/mcarneiro_ • 1d ago
r/calculators • u/gorunannno • 1d ago
Hello, was wondering if there is anything like this https://imgur.com/a/niPtgSJ but for the 991 ex rather than 991 es? Nothing is labelled similarly inside the calculator (KO or KI) so I was wondering if anyone has already figured out how this works.
r/calculators • u/Embarrassed-Chain568 • 1d ago
I was charging by ti-84 plus ce and it was okay but about 2 hours later, I saw that the battery disappeared??? Like the green bar isn’t anywhere and my gc was really hot… I was using a charger that I had recently bought from a seller online, could that be the case?
r/calculators • u/old_paelzer • 1d ago
Bin am testen von RPN83P. Ich habe den Stack mit Zahlen gefüllt und ]2nd] [U] gedrückt für rolls up. Habe keine Reaktion bekommen/Stack hat sich nicht verändert. Wo ist mein Fehler? Was mache ich falsch?
r/calculators • u/MisterMike318 • 2d ago
Hi
My son's Casio FX cg50 back light has suddenly stopped working. Settings are at max but it doesn't change the brightness at all whether I go up or down so it's as if the backlight just isn't even working. Is there anything I can do to check what could be wrong? Is there a repair for this? I have seen there are screens available on AliExpress but would this solve the problem and is there a teardown video anywhere? I've got some experience with soldering and can definitely do a screen swap if it's a case of tearing down and replacing the screen via a ribbon cable (like on a Gameboy which I've done before). Any help would be great because I'm sure you know these things aren't cheap or easy to get hold of.
Thanks in advance
r/calculators • u/clickbangj • 3d ago
I've had this one for a while. Still works. No issues. I've upgraded since but still enjoy it.
r/calculators • u/Iceburgh-Lettuce • 2d ago
Hi all,
My fx-CG100 has a little issue where it's not giving me several answers in surd form and won't let me convert. For example, when I input 4x4-31x3-31x+4=0 into the polynomial function, the answers should be 4 ± √15, but the calculator doesn't output these! It just gives the unsimplified number...
Even worse is that the two non-real answers are also in surd form but present perfectly fine!
Any way to fix this? I've had this issue with π answers too...
r/calculators • u/No_Scratch_386 • 2d ago
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I need help with my calculator my calculator screen has strips and i cant see my numbers properly i need advice how to fix this
r/calculators • u/Complete_Rabbit_844 • 2d ago
r/calculators • u/Saft_Rex • 2d ago
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It keeps doing this but I really need it for school
r/calculators • u/Distinct_Hold_3656 • 2d ago
r/calculators • u/lz1aam • 3d ago
Hi everyone!
I've been working on a native Linux emulator of the Soviet Elektronika MK-61 and MK-54 programmable RPN calculators.
These machines are an interesting part of calculator history. They have their own programming model, unusual numerical behavior, and some fascinating hardware quirks.
My goal was to preserve the authentic calculator behavior while creating a comfortable desktop application for Linux.
The project uses the original EMU145 microcode emulation core and a custom C++20 / Qt 6 interface.
Some features:
It's still a work in progress, but I'd love to hear what other RPN and vintage calculator enthusiasts think about it.
GitHub: https://github.com/lz1aam/elektronika-mk61
I'm particularly interested in feedback from people familiar with the original Elektronika calculators or other classic programmable RPN machines.