Casio FX-991EX Engineering/Scientific Calculator, Black, 3" x 6.5" x 0.4"

I have grown up using casio calculators and Casio itself is a famous brand. I find this calculator is more user friendly and easy to operate than most of the similar calculators from other brands. Hands down FX-991 series is one of the best scientific calculators.

I love Casio calculators. This one has a great look and feel. The display is roomy enough for most ready calculations and has a nice font. The calculator can do statistics, curve-fitting, integration, etc. to fifteen decimal places, as well as all the scientific functions (except hyper trig). The CPU is fast. The fx-991EX is an evolution of the decades-old Casio design, carried to near-perfection. Compared to the (not much) cheaper fx-115ES PLUS, the fx-991EX is faster, can do more and has a better display, but unlike the less expensive fx-115, the fx-991 has no hyper-trig functions, no Abs(), Int(), Intg() {i.e. floor()}, LCD, or GCD functions, nor does it do unit conversions. The fx-991 is my go to, but I'm glad I have both, as well as the programmable fx-9750GIII. The solar cell works very well. The LR44 battery will need replacing after a few years.

Unless you want to graph functions, this device has all the functions you need, and a lot of thought went into making this device. Even though the key layout would have been better, it is a perfect calculator for engineers. The power doesn't remain on for so long when you don't use it for a considerable amount of time, like if you're thinking of how to solve a problem just after finish punching in the numbers for the last question, by the time you have to use your calculator again, it is off. It could just be me being slow at thinking but I had no problem like this with TI-84 before.Another thing is that the answer button recalls the very previous answer, not the answer I want to bring. For example, if I entered a complex calculation and I have to finally test some simple multiplications, if I press = button to test one and press AC, the Ans button will bring the product of a complex calculation and the multiplication, not just a complex calculation. There's a little bit of learning curve if you're coming from TI calculators. Finally, the footing needs some sort of rubber padding to keep the calculator stationary. It is impossible to lay it down on the desk and try to punch in numbers because it gets so wobbly. I always have to hold it in my hand to keep it from moving.

I am a graduate student. I have been using a fx-991ES Plus (European/Asian model) that I bought when I was in undergrad. It's been 9 years now. There was no issue with that calculator except that I did not like the buttons and its slow performance. So, I decided to try this US model fx-991EX Classwiz and compare it with the fx-991ES Plus myself. After several weeks of use, I realized that this calculator is technologically far more advanced than a fx-991ES Plus.FUNCTIONS: Many extra functions on top of fx-991ES Plus that are very useful. See the manual or compare in the original product website to get more details on this.EASE OF USE: The buttons are more ergonomic, responds to press more effectively.PERFORMANCE: Extremely faster than fx-991ES Plus, exactly what I need for a PhD comprehensive exam.DISPLAY: Larger display and better shaped fonts make it easier to read. I love the icons display of the main menu.CONSTANTS & CONVERSIONS: No more taking off the back cover and looking up constants/conversions from a list. It has all constants and conversions categorized by types in the options menu, making it much easier to find.Overall, I am very satisfied with my purchase. It is worth every penny.

#1 Pro:The best thing about this calculator to me, by far, is how it minimizes inputs for evaluating formulas.Example: AX^2 + BX + C -> Calc KeyWill open a prompt asking for A, B, C, X and will even accept expressions and evaluate them before putting them into the equation. Feels several times faster than the old way of storing values into A, B, C, X and then constructing the formula you want to evaluate. Also makes it VERY FAST to guess roots of a polynomial or solutions for linear combinations of sine and cosine.#2 Pro:Pressing left at the beginning of a line jumps to the end. Pressing right at the end jumps to the front. It seems like a small thing but it cuts down on keypresses compared to having to press Shift -> L/R.#3 Pro:Processor speed is nice. Definitely look into this one if you're doing a lot of definitive integrals.#1 Con:Lose your stack anytime the calculator goes into sleep mode. Lose your stack if you switch modes. Lose your stack if you power off. The only reason I can imagine this is done is due to testing board standards in countries where this calculator is the top dog because it is HORRIBLE. Enough for it to feel like the first mode is the only thing that exists. Enough for me to hesitate using it for an important test.#2 Con:Constants are only referred to by their symbol. Other calculators will print out their name while you are selecting them. Huge liability if you're the forgetful type and a nasty surprise on a test if you learned from a teacher or textbook that used a different symbol.#3 Con:No RREF for matrix mode for some reason? You can use the system solver for up to 4x4s, but it's still very odd. Couple that with memory loss due to switching modes and I don't see a reason to pull this out over other calculators when dealing with Linear Algebra.

This is a very good calculator. I use it for much of my projects that require extensive math. If I had to do the math by hand, it would take me a lot longer to accomplish.

This calculator is so compact, and so useful. I would pay $500 for this calculator if it was the only way to get it.

I like everything about this product.

Es una calculadora que se siente profesional, no se siente plasticosa y cuenta con muchas funciones utiles en las ingenierías o para tu trabajo. 10/10

Calculadora mega completa em termos de funções disponíveis nela. Precisa de um pouco de estudo para aprender a trabalhar com todas as funcionalidades, o básico da calculadora é bem fácil de se usar. Muito bem acabada e bonita.

Perfect for engineering tasks

Studeer je elektrotechniek? Koop dit apparaat!Deze rekenmachine is toegestaan op de tentamens, omdat het geen grafische rekenmachine is.Wel heeft de rekenmachine de functionaliteit om matrices te vermenigvuldigen, bepaalde integralen te berekenen, a+bj en modulus hoek notatie en ga zo maar door.Het scherm heeft een hoge resolutie en is goed leesbaar, zie geen redenen om deze rekenmachine niet te kopen.

Muy bueno el producto, llego muy rápido.