If you've just bought a scientific calculator, or got one at school, and it's full of buttons, half of which are unfamiliar — don't worry. This guide is exactly for you. We'll go through everything a beginner student needs to know: from the basics, through trigonometry, to solving equations. We'll use the Casio FX-991 series as a reference, as it's the most common in Hungarian secondary schools, but most functions work similarly on other brands.
Tip: If you don't have a physical calculator at hand, try our scientific calculator online — with the same functions, right from your browser.
What is a scientific calculator and how is it different?
A scientific calculator (scientific calculator) differs from a regular school calculator in that, beyond basic operations (addition, subtraction, multiplication, division), it also has trigonometric, logarithmic, statistical, and equation-solving functions.
Who should use it?
- Secondary school students — for math, physics, chemistry classes and for the final exams
- University students — in engineering, economics, and IT programs
- Adult learners — evening school, online courses, self-study
The Casio FX-991CE X is so popular in Hungarian schools because it's reliable, includes all necessary functions, and can be used in final exams.
Get to know your calculator
The first step is to know what each button does. Here are the most important ones:
- ON / AC — Power on and clear the display contents
- SHIFT — Access secondary functions (yellow labels above the buttons)
- ALPHA — Tertiary functions (red labels), such as memory variables
- MODE — Switch modes (DEG/RAD, EQN, STAT, TABLE, etc.)
- S↔D — Toggle between fraction and decimal form
How to switch modes? Press the MODE button, then select the number of the desired mode. For example, you work in DEG (degree) mode for trigonometry, while in EQN mode you can solve equations.
Basic operations and fractions
The scientific calculator automatically follows the order of operations (parentheses → powers → multiplication/division → addition/subtraction). This means that if you enter the expression 3 + 4 × 2, the result will be 11, not 14. If you want a different order, use parentheses.
Entering fractions: You can enter fractions with the a b/c button. For example: 2 a b/c 3 = ²⁄₃. If you want to convert it to a decimal, press the S↔D button.
Related: If you're calculating percentages, check out our percentage calculator as well.
Powers, roots, and trigonometry
Exponentiation and root extraction:
x²— squaring (e.g., 5² = 25)√— square root (e.g., √25 = 5)x^y— any power (e.g., 2^5 = 32)SHIFT + √(x√) — any root
Logarithms:
log— base-10 logarithmln— natural logarithm (base e)
Related: Use our logarithm calculator for practice.
Trigonometry (sin, cos, tan): The most important thing you need to know: always check whether you are in DEG or RAD mode!
- DEG (degrees) — use this for high school math and the final exam
- RAD (radians) — for more advanced math and physics
If you calculate sin(30) in DEG mode, the result is exactly 0.5. If you are in RAD mode, you get a completely different number.
Inverse functions: SHIFT + sin = sin⁻¹, SHIFT + cos = cos⁻¹, SHIFT + tan = tan⁻¹.
Try it live: A our scientific calculator helps you practice trigonometric calculations.
Solving equations (EQN mode)
One of the most useful features before the final exam:
- Press the MODE button
- Select the EQN mode
- Enter the equation type (e.g., quadratic: ax² + bx + c = 0)
- Enter the coefficients (a, b, c)
- The calculator displays the solutions (x₁ and x₂)
Example: x² − 5x + 6 = 0 — a = 1, b = −5, c = 6 — Result: x₁ = 3, x₂ = 2
You can also solve linear equation systems with two or three unknowns in the same way.
5 common mistakes every beginner makes
- Ignoring the order of operations — If you enter the expression 3 + 4 × 2 without parentheses, the machine calculates according to mathematical rules.
- Mixing up degree/radian mode — Always check the top of the display to see if DEG or RAD is shown.
- Forgetting the operation mode — If you want to calculate statistics, don't try it in normal mode. Switch to STAT mode.
- Incorrect entry of negative numbers — The (−) button (negative sign) is not the same as the subtraction button (−).
- Failing to clear the memory before the final exam — Press: SHIFT → 9 → 3 → =.
Frequently Asked Questions (FAQ)
How do I turn on the scientific calculator? Press the ON or AC button.
Why am I getting incorrect results for sin/cos calculations? You are probably in RAD mode instead of DEG.
Can I use the Casio FX-991 on the final exam? Yes, the Casio FX-991 series is allowed in Hungarian final exams.
What is the difference between a scientific calculator and a regular calculator? A scientific calculator can also handle trigonometric, logarithmic, and statistical functions.
How do I solve a quadratic equation with the calculator? Switch to EQN mode (MODE → EQN), select the quadratic equation option.
Why is the order of operations important? Because the calculator automatically follows mathematical rules.
Summary — 3 steps to become a pro
- Get to know your calculator — Know where the SHIFT, MODE, S↔D, and (−) buttons are.
- Practice with exam tasks — Solve 5-10 old test papers with the calculator.
- Use the online version — If you don't have the physical device, practice with our scientific calculator in your browser.
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