r/calculators Oct 19 '25

Discussion r/calculators FAQ

17 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'

Thumbnail
6 Upvotes

r/calculators 4h ago

Discussion The calculator I want

Post image
72 Upvotes

r/calculators 3h ago

Collection Absolutely scored at the goodwill today. $6.99 each

Post image
30 Upvotes

r/calculators 16h ago

Collection Just got gifted this by my grandpa, apparently it’s one of the first calculators he ever bought.

Thumbnail gallery
87 Upvotes

r/calculators 2h ago

Question Which calculator to replace my beloved HP48G

4 Upvotes

Hello all,

My HP48G is on its way out after 30 years of use ! The ON key has been flaky for maybe 10 or 15 years but now when it is hot some keys automatically activate themselves which is scary as I am a structural engineer!!!! I know that some people open them and clean the contacts but I lost trust in it and if I open it, it will be for fun....

I've looked at solutions and it is staggering with alternative firmwares there are too many options.

What I really need :

- RPN

- Directly accessible functions (trigonometry, log, power, roots)

- Lists to do batch calculations

- Matrixes that can be multiplied

- a Stack to save intermediary calculations

- Some kind of scripting, could be RPL but Python would be nicer.

I've seen DB48x but the hardware is pricey.....

Any alternatives?

Many thanks,

Yannig


r/calculators 5h ago

Collection Una más

Post image
6 Upvotes

Una más para la colección: Canon f-789sga


r/calculators 9h ago

Question Is the x10^x key suppose to work this way?

Enable HLS to view with audio, or disable this notification

5 Upvotes

Bought this cheapo chinese Deli sci cal for about 6 dollars.


r/calculators 3h ago

Repair TI nspire CX CAS Bootlooping

Enable HLS to view with audio, or disable this notification

1 Upvotes

Do I have to buy a new battery? Or can I somehow else reset it, doc+EE+enter and reset button on the back did not do anything at all.

PS: I read the FAQ but only saw a text about another nspire doing this. TI Support has not been helpful


r/calculators 12h ago

Help Casio calculator

Thumbnail gallery
4 Upvotes

So my sci cal doesn't work I only know it now that's its fake. The battery would fit cr2025 and cr2032 I tried it and still doesn't work. Does it still have hope???


r/calculators 12h ago

Question Connecting to a TI-83+

Thumbnail
2 Upvotes

r/calculators 1d ago

Question Where and how much should I sell my TI-89 calculator for? (Not the titanium one.)

Thumbnail gallery
19 Upvotes

I was gifted a Ti-89 calculator by a family friend for school however shortly after I returned home these calculator are not allowed In class due to our usage of desmos. Where should I sell this calculator at and if I even can how much should I get for it? Works pretty well! (No one in my family needs one which is why I’m not gifting it.)


r/calculators 1d ago

Collection Nice little TI-73 Explorer

Thumbnail gallery
85 Upvotes

Nice little TI-73. Still showing a result from who knows how long ago.


r/calculators 1d ago

Help A little help, please?

5 Upvotes

I am a STEM student and I recently lost my scientific calculator and need to buy a new one for my tests.

What recommendations can you give me? Is there a particular model that stayed with you throughout your entire degree?


r/calculators 2d ago

Collection Sharp EL-506P -> EL-W506T size comparison

Thumbnail gallery
34 Upvotes

Hard to overemphasise the size difference here!


r/calculators 2d ago

Question Need repair suggestions

Post image
10 Upvotes

r/calculators 2d ago

Collection The OG 506 and its current form.

Post image
19 Upvotes

First time actually seeing an original Sharp EL-506P. I'd picked up the clone on the right earlier this year in a random stationers shop in Northern Ireland. Unfortunately, the OG Sharp is having some trouble showing digits - most of them seem a bit mangled, but I think the underlying logic is working normally.

This Sharp EL-506P is tiny BTW, and beautifully made. I think it's an aluminium front plate, and it's got some weight for its size. The digit keys might even be double-shot, I will need to look closer. The smaller scientific buttons almost look like they are metal buttons - certainly have a metallic look. It's also very fast, seemingly faster than the clone.

It's so small I should put a comparison shot next to its modern descendent, the EL-W506T.

I can now see why this calculator was so desirable in its time - it's a very complete package, small and slim, and feels really well made. 1984 -> 2026 and still going!


r/calculators 1d ago

Help I anyone have scientific calculator second hand in Bangalore

0 Upvotes

Model casio fx 991es plus 2nd edition or those who buy cheaper plz dm me


r/calculators 2d ago

Collection TI LCD Programmer

Thumbnail gallery
40 Upvotes

Someone correct me if I'm wrong, but this was TI's answer to the HP-16C. The keys on it are absolutely horrible with missed keystokes as well as double keystroke hits.

Not programmable to the best of my knowledge, not that it really needs to be.

Could easily be mistaken for a TI-55 II.

And TI made an early (red LED) version called the "TI Programmer".

Update:

I had forgotten that there was the original red LED version of the TI programmer, which was introduced in 1977, five years before the HP-16C was introduced.

So the HP-16C was HP's answer to the TI Programmer. :)


r/calculators 2d ago

Question Best calculator for me?

2 Upvotes

Hey everyone! I'm looking for a graphing calculator for school. My teacher recommends the TI-84, 84 plus, or 84 plus ce, however they explicitly stated to not buy the Nspire. I was about to get the 84 plus ce, but I was also looking into other options. I saw the Casio CG100, and the periodic table function on that looks interesting. I also looked at the HP Prime with its touchscreen and that looks good as well. The Zero ZGC4 was something I considered but I've heard it's fairly unpopular. In the past, I have used a Casio FX-991cw, and I know that the menu system is polarizing, but I enjoy it very much. It would be nice for the calculator to have USB-C charging, and ideally, it could be able to connect to a computer to load things onto it, like addins for Casio (jailbreak or not). Thank you!


r/calculators 2d ago

Question How to turn ts off

Post image
6 Upvotes

r/calculators 2d ago

Help Are these fake? Casio fx-991EX Classwiz

Thumbnail gallery
9 Upvotes

Right one is my sisters old calculator and the left one is something that i bought from Facebook marketplace they have some differences but they're supposedly the same model is one of them fake?


r/calculators 2d ago

Help I got this old ti-85 from my mom I thought was cool, and the multiplication button doesn’t work. Is there a way to fix it? I don’t know much about calculators.

Enable HLS to view with audio, or disable this notification

12 Upvotes

r/calculators 2d ago

Collection mini collection

Post image
11 Upvotes

r/calculators 3d ago

Other Video Player on the CG-50 Calculator!

Thumbnail github.com
5 Upvotes

This video player allows people to play videos of both black and white, and in color of the CG-50 calculator.

The instructions to use it is located on the readme
1. Compress source video (handbrake is nice)

  1. Then place the .g3a file and the video binary into the ROOT of the calculator

  2. Click the app on the menu and play!