Product Comparison: Casio FX-115ES Plus vs Casio FX-991ES Plus

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General Specifications
FX-115ES Plus
FX-991ES Plus
About the Product
Casio’s latest and most advanced scientific calculator features new Natural Textbook Display and improved math functionality. FX115ES PLUS has been designed to be the perfect choice for high school and college students learning General Math, Trigonometry, Statistics, Algebra I and II, Calculus, Engineering, Physics.
The Casio FX-991ES Plus is Casio's most advanced scientific calculator with 417 mathematical functions. Recommended for Advanced GCSE, A/AS Levels and Highers. Dual powered (solar with battery back-up). This advanced model allows Matrix, Equation, Integration and Differential calculations as well as Random Integers, Scientific Constants and Metric Conversions. The large natural texbook display (Natural V. P. A. M. ) shows mathematical expressions as they appear in your textbooks. Suitable for GCSE, A Level and above.
Size & Weight
6.38 in.
6.38 in.
3.15 in.
5.51 in.
0.44 in.
3.15 in.
3.4 oz.
3.84 oz.
What customers say about "Size & Weight"
Casio FX-115ES Plus Pocket, Battery/Solar, Scientific calculator, Purple, Silver, Plastic
  • Used this for my licensing exam. Calculator works great. Powerful calculator for its size.
  • I needed this calculator for my math course and it works really well and the size of it fits into my bag nicely.
  • The buttons on the keypad are a perfect size so that you will not accidentally select another unintended button.
  • It is simple to use and light weight. Color is good. No place to complain. Thumbs Up.
  • Uncomfortable sizes sometimes make it difficult to carry around.
Casio FX-991ES Plus Scientific calculator
  • In addition to it's function, it also has a very slim design that fits well into both my book bag and my laptop case pockets. I would definitely recommend it.
  • The product is good and I love it. Because you can easily take it with you to study and not think about how convenient it is or not.
  • It's light and does everything it is meant to do.
  • Very light. When carried with you, its weight is not felt. You can always take this with you.
  • If you do not use the bag, then it will be inconvenient for you to carry this calculator with you.
Display Type
Display Size
96 x 31 pixels
96 x 31 pixels
Touch Screen
What customers say about "Display"
Casio FX-115ES Plus Pocket, Battery/Solar, Scientific calculator, Purple, Silver, Plastic
  • Display is nice and roomy for the price unlike most devices within this price range.
  • The way the equations are displayed make it easy to read to ensure the correct information was entered.
  • The display is very simple and clean, you can apply complex/long equations easily like how you would write it on paper.
  • The display is clear and easy to read, and the keys have a nice feel to them with just the right amount of snappiness.
  • It's a scientific calculator. The display is nice and shows equations. There are alot of options for how to display results, decimal vs fraction vs improper fraction vs radians and so on.
Casio FX-991ES Plus Scientific calculator
  • It is very helpful with calculating from simple math to advanced engineering problems, as it has many functions and have natural display.
  • The key that I love is the natural display. What I see on the screen is what I meant to type in. With many other calculators my intent and what I enter are two different things.
  • The display is excellent. I can easily see it in direct sunlight.
  • I like that the screen size is large and it does not reduce anything.
  • Worked fine for 3 weeks then developed some sort of fault. The LCD panel stayed blank upon pressing the power button.
PC Connectivity
Battery Type
LR44 (GPA76) x 1
1 x LR-44
Pre-Loaded Applications
All General Mathematics courses, Pre-Algebra, Algebra I & II, Polar, Statistics I/II Var, Pre-Calculus, Trignonmetry, Chemistry, Physics, Engineering
Integration, Complex number calculations, Differential, Vector, Matrix operations, Equation calculations, Integration/Differential
Natural textbook display, Over 280 functions, Built-in solar cell, Simultaneous and polynomial solver, Matrix and vector calculations, Variable memory: 9
Built-in solar cell, Number of Functions : 417, Natural textbook display, 10 + 2 digits, Dot matrix display, Plastic keys, Variable memory: 9
What customers say about "Features"
Casio FX-115ES Plus Pocket, Battery/Solar, Scientific calculator, Purple, Silver, Plastic
  • This is a really good scientific calculator for any college student in Algebra and Pre-Cal. I found it having the same features but easier to use than the TI-36X Pro.
  • Like any graphing calculator, the Casio lets you store lists of data, fit regression curves, and see 1- and 2-variable stats.
  • It does things that the TI-84 doesn't do, such as finding the inverse regression equation A + B/x for paired (x, y) data.
  • Buttons and UI can be a little overwhelming at first glance if you're used to the simplicity of the TI-XX family.
  • Buttons are very flimsy and cheap. Seems low quality.
Casio FX-991ES Plus Scientific calculator
  • I am using this calculator CASIO FX991ES PLUS mostly for complex number operations and it works great, no issues. I am simply happy with it!
  • I use it beside my Ti 84 plus for engineering. And have to say that this is a charm almost 7 years using, no battery change, or problems.
  • It has been two years already but it still works fine, and I have not yet replaced the battery since buying it.
  • Works great. I needed an advanced calculator that didn't have a programmable memory like the TIs do. The university didn't allow them. This fit the bill perfectly.
  • It counts for a very long time. I don’t know what it is connected with, but it is sometimes annoying.
Warranty / Certifications
Manufacturer Warranty
1 year(s)
1 year(s)
Other Information
19.79 $

Other reviews