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 • • 1h ago

Other fx-100W

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• Upvotes

26 years, 2nd battery.

P=0,1mW


r/calculators • • 2h ago

Help Calculators at too small

4 Upvotes

I wanted to calculate (70.1*10^12)^150000 and every single calculator told me infinity or too big ):


r/calculators • • 12h ago

Help Best non-programmable calculator for 4×4 matrices and 4-variable equations (excluding the fx-991CW)?

8 Upvotes

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 • • 1h ago

Question HP Prime or TI Nspire CX II CAS coming from Desmos?

• Upvotes

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 • • 9h ago

Question Why the heck does the NCESS allow the 911ex and the TI36x but won't allow any other HP calc besides the 35 and 33?

3 Upvotes

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 • • 14h ago

Help Changer la batterie de la NumWorks

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6 Upvotes

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 • • 17h ago

Question What are your favorite graphing calculator shortcuts?

9 Upvotes

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 • • 14h ago

Question Is there a way to run neo geo packet (color) games on a ti nspire cx

2 Upvotes

see title


r/calculators • • 1d ago

Help How to get table mode on this calculator?

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9 Upvotes

Please help I am not able to find this mode.


r/calculators • • 1d ago

Collection One small tool, seven graphic calculators

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161 Upvotes

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!

https://github.com/paxis76/el2-roi-calculators


r/calculators • • 22h ago

Question How to locate the serial number for Casio fx-991 cw?

3 Upvotes

I tried checking it's authenticity via qr but the website is down


r/calculators • • 1d ago

Announcement HP-17B

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30 Upvotes

Manual for someone who would enjoy it, pay shipping and what you think is fair.


r/calculators • • 1d ago

Collection Una más: TI-Nspire CAS

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29 Upvotes

r/calculators • • 1d ago

Other 1980s Casio calculator watch

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22 Upvotes

1st time seeing this 80 version. Operation push buttons on the side!


r/calculators • • 1d ago

Help TI-84 Probability Function

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8 Upvotes

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 • • 1d ago

Help Casio hr 16bk

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6 Upvotes

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 • • 2d ago

Help casio fx 300es plus

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14 Upvotes

what happened to my friend and can it be fixed?


r/calculators • • 1d ago

Announcement I want to buy scientific calculator if anyone from india want to sell a second hand scientific calculator dm me.

0 Upvotes

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.


r/calculators • • 2d ago

Help Hp prime “clearing memory”

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7 Upvotes

every once in a while when i turn on my hp prime it shows this screen, and no buttons work and turning it off and on with shift-on doesn’t do anything. what do i do to fix this?


r/calculators • • 2d ago

Question Calculator Store shipping

3 Upvotes

Did anyone who purchased a 16c from The Calculator Store used the pre-pay tariff shipping option to ship to the US still get a bill from FedEx after receiving their 16c.


r/calculators • • 2d ago

Question Game reccomedations for ti nspire cx

6 Upvotes

I have a ti nspire cx with a few emulators (gba, sms/gg, genesis, snes) and i have crafti (minecraft clone) and angry birds. Dou you have any recommendations for games

PS. Does anyone know if i can emulate ngpc on it?


r/calculators • • 2d ago

Collection [ Removed by Reddit ]

0 Upvotes

[ Removed by Reddit on account of violating the content policy. ]


r/calculators • • 3d ago

Discussion I ported Super Mario 64 to the Numworks N0120

83 Upvotes

The game runs baremetal and uses almost the entire external flash and RAM. The renderer still has a few issues but the entire game is playable on real, physically unmodified device at a stable 30fps, at the cost of a reduced 3D resolution and with some visual effects missing.

The game is only playable for the N0120 model as it has a much more powerful CPU and more than twice the amount of RAM of the N0110.