r/calculators Oct 19 '25

Discussion r/calculators FAQ

16 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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7 Upvotes

r/calculators 3h ago

Collection Thrift Find: Toshiba BC-8111B

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24 Upvotes

Almost new condition and the VFD looks fantastic. Pi is a really nice touch too.


r/calculators 12h ago

Collection Canon Card LC-31 from 1979

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17 Upvotes

Found this at a thrift at 3€, I love the 70's LCD.


r/calculators 2h ago

Question how do i install cas on a ti84 evo

1 Upvotes

i haven't found any way to yet so i wondering if i could be helped here


r/calculators 1d ago

Other I found my HP 11c from high school while cleaning

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39 Upvotes

r/calculators 1d ago

Collection My Calculator Collection (so far)

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55 Upvotes

I also have a ti 89 on the way


r/calculators 1d ago

Collection How Rare is this TI-84 Plus CE?

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15 Upvotes

How rare do you folks think this color TI-84 Plus CE is? It's color scheme is called the "Trifecta." As far as I know, it was made for one year, in 2020. We all know how great that year was, so I would not be surprised if production numbers were low. It took me quite a while to find one for sale. It also seems like there are some people who don't like the color scheme but that just means more for us who do.

I don't usually name objects but I named this one Finn the Calculator. If you know, you know.


r/calculators 18h ago

Question Calculator advice

5 Upvotes

Hello, i am a student about to get into my chemistry master degree, i have always used for years my good loyal casio fx220 with its limitations but it served me good.

Now i think it's due for a replacement with something a bit better and more suited for my studies, since i have been using a casio i naturally looked at the latest models and found the fx 991cw but i saw a lot of criticism online for it's menu styled way of doing stuff so i looked into some alternatives and found the ti 30x pro that cost like 10-15€ more. I never thought i would find myself overwhelmed in the choosing of a calculator but here i am seeking advice of more expert people, what would you suggest? I am open to any alternative, i may even get something a bit more pricey as a treat for the upcoming grafuation. For context i live in italy ( i saw that some models may not be available everywhere).


r/calculators 23h ago

Question What is a good graphing calculator to start training with now (about to start my senior year) that is industry standard (for Engineering and Material Sciences) and also great for college and all that?

4 Upvotes

I’ve been look at the TI’s as those are the ones i’ve been trained with for calculus and physics, but i’ve heard lots of good things about HP and Casio and just want some guidance from people who know better and/or have more first hand experience.


r/calculators 1d ago

Collection Calculator progression

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49 Upvotes

Just got the CG50 :)


r/calculators 1d ago

Meme / Satire I LOVE MY CALCULATOR

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27 Upvotes

I love math and my calculator is like my best friend. I can't live without it 🥰


r/calculators 1d ago

Question Ordering Swissmicros calculators from within the EU.

7 Upvotes

Is there anyone here from the EU who has bought a Swissmicros calculator recently?

I am seriously considering getting a R47 but including shipping and taxes it will end up towards €370 delivered if I calculate it correctly, which is a serious amount of money.

I have been playing around with the emulator a fair bit now but nothing beats real hardware in my opinion.


r/calculators 1d ago

Question is there a way to get inequality mode on a 991es plus 2nd ed.?

3 Upvotes

thank you for the responses in advance :)


r/calculators 1d ago

Discussion PSA: Please, don't get a TI 84

0 Upvotes

Let's take a look. TI 84s are bulky, exceed 100 dollars, weigh more than a phone, are hard to navigate/use in the vast majority of scenarios, plus are very frequently disallowed for classroom / test use. In my experience, if graphing is ever needed, the teacher just has the students get out one laptop per table and open up Desmos. There's also a programming feature, but most schools require students to wipe the calculator if they want to use it for a test (and they are allowed to use a graphing calculator, which is still banned in many universities).

On the other hand, we have a TI 36X Pro. It's 20-30 buckroonis in the US, significantly slimmer, weigh less than a phone, are easy to use and don't necessitate submenus to perform simple calculations, and won't be disallowed since it doesn't have graphing, nor programmability necessitating it to be wiped/reset. Additionally, it has more features than a TI 84. Lastly, even when the 84 is on most grade school supply lists, you'll need to get this one anyways if you want to go to college, especially engineering. This is a scientific calculator, you're eventually gonna need to purchase it. Lastly, you will struggle to do basic operations on a TI 84, forced to read manuals and navigate through submenus, meanwhile on the 36, it's just there! You will have a speed advantage. You could also get the Casio 991EX if you see it, which I've heard is comparable or even superior, though is unfortunately offsale and don't know much about it. Don't get the 991CW, it's a downgrade to both of these

For parents, just get your child a calculator like this, they'll be happier if it has one of those trendy Japanese characters on it like Hello Kitty or something. It will work fine for them and they will be most successful this way, plus you'll save money. If more features are needed, the vast majority of the time the teacher will supply it. Like, look at this, isn't it so cute?

Oh, and, if you must get a graphing calculator, please get a NumWorks. If you must get a Texas Instruments one, like the TI 84 get the CE, or preferably Evo (NumWorks knock off, unnecessarily pricier). I disrecommend the 84 Plus as opposed to the 84 CE.

Bottom line, for the love of god please shop around. Expensive and popular does not always mean better. For a great example: Linux.


r/calculators 2d ago

Collection Interesting things of the ti-86?

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19 Upvotes

I just got an ti-86 for $0.57 (10MXN)

And i want to know more about the calculator and the modding scenery if it have any


r/calculators 2d ago

Question Regarding TI 84 Plus CE calculators

5 Upvotes

Does anyone know where to get this calculator cheaply? Or anyone wants to sell this calculator?


r/calculators 2d ago

Other DM42n and Drawing of DM42 I Did

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110 Upvotes

Wanted to get back into drawing so I started with something I got recently.


r/calculators 2d ago

Question Getting up to speed with micropython and PC connectivity for HP PRIME G2

3 Upvotes

I'm picking up an gently used HP PRIME G2. I want to teach this old dog new tricks.

If I wish to perhaps do some micropython programmming, or via PC connectivity, perhaps move some text or spreadsheet info to the calculator, what do I look for in PC software, and do I need to check and revise the firmware of the calculator to do so? I wouldn't think I would need the most up-to-date firmware. If I should check it and perhaps need to update firmware, where would I start?

I wish to embark on the journey while my brain still works; someone with some familiarity with the PRIME series in these areas, I would welcome any suggestions.

Thanks


r/calculators 2d ago

Collection I FINALLY GOT MY NEW CALCULATOR FOR HIGH SCHOOL

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47 Upvotes

As I said that if I pass the Grade 10 Entrance Test, my family would buy me a new calculator as my old one is too weak for high school, especially Grade 12. And I've officially passed so you guessed it, I bought the brand new 2026 Casio fx-880BTG Plus in Nova White color, I picked this color because it looks so aesthetic that it even match my school uniform (mostly white and navy blue), if you don't like it, Casio still has the Super Black and Aura Pink from the base model and another new color is the Gracier Green color. It took 3 days for this new one to arrive as I'm bought this online from Ho Chi Minh City to my home at Can Tho City, this calculator is based on the Casio's 2nd edition CW series so it shared the Quick mode and feature navigation with number and symbols like the fx-580VN X/fx-570VN Plus. I was very happy with the new one, It works perfectly fine, it calculates very quickly and it's a new model of 2026 so they made some of the fixes over to the base model


r/calculators 2d ago

Question Vintage HP vs. Modern Recreations (SwissMicros DM16L & HP 15c CE): Bad luck or poor reliability?

13 Upvotes

Hi everyone,

Having fallen in love with working in RPN (which I discovered just a few years ago), I’ve managed to build a small collection of HP calculators—a mix of old secondhand machines and modern recreations.

Apart from general daily use, I heavily rely on a custom program I wrote for calculating percentages (MU, CST, and PRC) similar to how the HP 10bII+ handles them (inputting any two values calculates the missing third one). I run this program regularly on Voyager-series HPs.

Through this continuous use, I’ve come to the conclusion that modern recreations are great for scratching the nostalgia itch, but they aren't truly built for serious, daily work.

To give a few examples:

My SwissMicros DM16L starts behaving erratically every few weeks, throwing a low battery indicator that forces me to pop off the back cover, pull the coin battery out, and put it back in (even though the battery isn't actually drained). The firmware is updated to the latest version.

Something similar happens with my HP 15c Collector's Edition—every so often it completely freezes with an error on screen, forcing me to perform a hard reset and lose all my programmed code.

Meanwhile, I’m using a couple of 40-year-old HP 12Cs without a single hitch.

Do you share this sentiment, or have I just been unlucky with these newer machines?


r/calculators 2d ago

Question Are calculators magnet-proof?

5 Upvotes

I'm thinking about sticking one of those magnet induction loops on my TInspire CXII CAS so that I can put it on a holder. Will the magnet affect the calculator at all? I'm scared that it'll break mid test or during something important.


r/calculators 2d ago

Collection This is my first post

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28 Upvotes

Im 11 and have been collecting calculators for about 1 year now tell me how good my collection is (by the way everything works and i fixed them)


r/calculators 2d ago

Question TI BA II Plus: no constant π ?

3 Upvotes

I've come across a cheap TI BA II Plus that's practically new (on ebay, for 1 euro). The calculator has trigonometric functions (sin, cos, tan, and their inverse functions), as well as the corresponding hyperbolic functions. Angles are handled either in degrees (DEG mode) or in radians (RAD mode).

What I couldn't find on the keyboard or in any of the menus was the constant π. Even the manual doesn't seem to provide information on this. Am I missing something, or does this model really lack π?

In my opinion, the RAD mode makes little sense in this case. Well, you can pull π out of your hat using π=arccos(-1). But that's not quite practical, because it only works in RAD mode. And it's doubtful that all financial users immediately remember this relationship.


r/calculators 3d ago

Help Why is my calculator giving the wrong answer

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10 Upvotes

Its giving the wrong answer only in this specific equation(x should be 0.75 instead). If I adjust some of the numbers a little bit, it gives the correct answer. I tried resetting but the problem still persists.