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/Fair_Percentage_5565 • 11h ago
1917 + 50 = 1967, so I suppose it was made that year. It is a little loose due to wear, but that's actually nice.
r/calculators • u/Sequentialdays • 9h ago
Hello everyone! I found this $5 Canon OS-1200 at a thrift store, I know basically nothing about these but it is such a neat piece of tech I had to have it. Now in doing some googling I have not been able to find a user manual, year of production, or really anything about this guy. It seems to be working fine but I’d love a manual so I can go through and test all the features to make sure it’s in good shape! Any info about this model is appreciated!
r/calculators • u/Busy_Abalone8445 • 15h ago
My calc history:
Early 2020s:
Casio fx85MS
Short circuited by water
2023-24
Basic calculator
Internal damage
The CE, Dexin, and the Clone 991 in 2026
r/calculators • u/Every-Equipment-9393 • 1d ago
I wanted to calculate (70.1*10^12)^150000 and every single calculator told me infinity or too big ):
r/calculators • u/No_Comparison4153 • 23h ago
I have decided to get a graphing calculator, and I am stuck between the HP Prime G2 and the TI Nspire CX II CAS. I have used Desmos and a desktop calculator that had a basic CAS, so I want to buy a calculator which won't feel too different from that. I have been able to use the Nspire for a bit and the Prime through an emulator, and I did notice some differences between them.
The Nspire seems to be able to graph functions and points at the same time, while the Prime can only do one at a time, which is pretty annoying if it actually doesn't support that. It also doesn't seem to be able to find zeros or intersections or go to X or Y values precisely when in the advanced graphing mode, while the Nspire seemed to be able to do that when I tried it out. The Prime is also a bit confusing with its seperate "Home" and CAS modes (that share functions anyways so there's no point in seperating them??) and in the way that it has both lists and spreadsheets. However, the touchscreen and help system in the Prime is so much better to use than the Nspire's jumpy touchpad and the random menus of functions. I actually haven't really had any real problems with the Nspire document system, I just make a blank document if the scratchpad doesn't support a feature and then just delete it afterwards.
I was originally planning to buy the Nspire because it was recommended along with another TI calculator, but after checking here I decided to see how the Prime compared just in case it was actually better. I'm looking for something that matches the way Desmos works and the easy features it has the closest. Both calculators are approved and only differ in price by $10, so the only thing I'm comparing are their feature sets and the features I immediately noticed that felt different. Should I buy the Prime, or should I still stick with buying the Nspire?
r/calculators • u/FlipFlopFlopFlip_ • 1d ago
Recommend a good non-programmable calculator that can do 4x4 matrix operations and solve 4-variable equations. Please avoid recommending the Casio fx-9910CW. I used the EX version earlier. I hate this new CW one.
r/calculators • u/limon_picante • 1d ago
This is so annoying to me. The HP35 can't even do matrix operations natively yet other ones can? Why can't I bring my HP42s? It's certainly not as advanced as some of the others they allow. Am I missing something here?
r/calculators • u/Caro_maths • 1d ago
Bonsoir,
J’ai ouvert la NumWorks pour changer la batterie mais je n’arrive pas à démonter celle qui est dessus car elle est collée.
Savez-vous comment faire svp?
r/calculators • u/Real-Hair6810 • 1d ago
I've been exploring the features of graphing calculators and realized there are probably many useful shortcuts that beginners don't know about.
What's one calculator shortcut or lesser-known feature that you find genuinely useful?
It could be something related to graphing, equation solving, statistics, or navigating menus.
I'd love to learn some tips from experienced calculator users!
r/calculators • u/Popular-Injury-2845 • 1d ago
see title
r/calculators • u/hello_unknown3256 • 1d ago
Please help I am not able to find this mode.
r/calculators • u/paxis76 • 2d ago
I play a lot of Endless Legend 2 on PC and kept asking myself the same question: if I buy this building or upgrade, how many turns until it pays for itself? So I built a little ROI (return of invest) calculator on HP Prime G2. Then it got a bit out of hand and now it runs on every graphing calculator I own.
In the picture (top left to bottom right):
- TI Voyage 200 – TI-Basic
- NumWorks – Python
- Casio Graph Math+ – Python
- TI-Nspire CX II-T CAS – Python
- TI-84 Evo-T – Python
- HP Prime – HP PPL
- TI-86 – Assembler!
The programs were written with a lot of help from an AI assistant (vibe coding). I'm currently relearning Python (I did BASIC, Pascal and Java a long time ago) by rebuilding the TI-84 version myself from scratch, which has been a great way to learn.
Happy to share the code or answer questions about any of the ports!
r/calculators • u/Many_Novel_9716 • 1d ago
I tried checking it's authenticity via qr but the website is down
r/calculators • u/Just_Be88 • 2d ago
Manual for someone who would enjoy it, pay shipping and what you think is fair.
r/calculators • u/TheCalcLife • 2d ago
1st time seeing this 80 version. Operation push buttons on the side!
r/calculators • u/Tradionalist_Calico • 2d ago
In my statistics class, we were assigned to do some probability simulations on our calculators. One of the questions was to find how many boxes it would take to get something that was in only 10% of boxes. Like I was shown I clicked MathPRBrandInt(1,100). However my calculator was only giving me numbers like what is shown in the image. I did get my calculator used and it does look like some code was manipulated but I was wondering if there is any way to fix this in the settings without factory resetting my calculator.
r/calculators • u/Maleficent-Data2709 • 2d ago
Hi, I’m having a problem with my Casio. I took it apart for cleaning and put it back together, but the movement isn’t working. Could someone help me reassemble it?
r/calculators • u/reddit05052112 • 3d ago
what happened to my friend and can it be fixed?
r/calculators • u/PresentationFull1812 • 2d ago
I am looking for a scientific calculator that is just as new as my university needs me to buy a new scientific but I was overconfidentlt told my friend who bought one for 1400 that i can buy the same thing for much less. If anyone will sell it please reply.
