How to Use a Calculator Correctly in IGCSE Exams

Written by · · Last updated · ~11 min read

A calculator can save time and reduce arithmetic errors in IGCSE Mathematics and Sciences — but only if it is the right type and you know the functions that examiners still expect you to understand. This guide explains which calculators are allowed, which features are strictly prohibited, and how to use the most useful modes: storing constants, solving polynomials, solving simultaneous equations, and finding the prime factors of a number.

Quick takeaway: For Cambridge IGCSE Mathematics (0580 / 0980) you need a scientific calculator without graphic display or CAS. The Casio fx-991EX / fx-991CW ClassWiz family is the safest widely available choice. Always show method; a correct calculator answer with no working scores zero method marks.

1. Which calculators are recommended?

Cambridge International does not endorse a specific brand. In practice, the following non-CAS scientific models are accepted at examination centres worldwide and cover every function needed for IGCSE Maths and the sciences:

Model Why it is suitable
Casio fx-991EX ClassWiz (or fx-991CW) Equation/Func mode (polynomials up to degree 4, simultaneous up to 4 unknowns), table, statistics, 47 built-in scientific constants, natural display. Widely recommended.
Casio fx-83GT CW / fx-85GT CW Standard school scientific calculator. Reliable, cheaper, sufficient for most IGCSE papers.
Texas Instruments TI-30X Pro MathPrint Scientific, no graphing, no CAS. Accepted alternative.

For the majority of students sitting Cambridge 0580 / 0980 or most science papers, a scientific calculator of the type above is the correct choice. Check your exact syllabus: Cambridge International Mathematics 0607 requires a graphic display calculator for some papers — that is a different qualification.

2. Features that are strictly prohibited

According to the Cambridge Handbook (Section 5.1.7.1), calculators with any of the following facilities are not allowed unless the syllabus specifically states otherwise:

  • Graphic display (graphing calculators)
  • Data banks
  • Dictionaries or language translators
  • Retrieval or manipulation of text or formulae (stored notes / formula sheets)
  • QWERTY keyboards
  • Built-in symbolic algebraic functions (CAS – Computer Algebra System)
  • Symbolic differentiation or integration (algebraic output, not purely numerical)
  • Remote communication (Bluetooth, Wi-Fi, infrared, etc.)

Do not buy a calculator that advertises “CAS”, “symbolic algebra”, “graphing”, “formula storage”, or wireless connectivity if you intend to use it in a Cambridge IGCSE examination. Even if a model can be put into “exam mode”, centres may still refuse devices that look like graphing calculators.

Pearson Edexcel IGCSE rules are broadly similar regarding CAS and text storage; some graphical calculators without CAS may be permitted under Edexcel, but they must have memory cleared. When in doubt, stick to a ClassWiz scientific model — it is safe for both boards.

3. Storing physics constants (and your own values)

On the Casio fx-991EX / ClassWiz series you have two practical options.

Built-in scientific constants

The calculator contains dozens of CODATA constants (speed of light, elementary charge, Planck’s constant, etc.). Typical access path:

  1. Press SHIFT then 7 (CONST) — or open the Catalog / Constants menu depending on model.
  2. Scroll or type the number of the constant you need.
  3. Press EXE to insert it into your calculation.

Useful for Physics and Chemistry papers when a constant is required but not printed on the question paper (or when you want a high-precision value).

Storing your own numerical values in memory

You may store numbers in letter memories (A–F, X, Y, M). This is allowed because the stored content is purely numerical.

  1. Calculate or type the value you want to keep (e.g. a measured average or intermediate result).
  2. Press SHIFT then RCL (STO), then the letter key (e.g. A).
  3. To recall later: press RCL then the same letter.

Never attempt to store text, equations as text, or formula sheets — that capability is prohibited.

4. Solving polynomial equations

ClassWiz models can solve polynomials up to degree 4 numerically. This is useful for checking roots of quadratic or cubic equations that appear in Maths or Physics (e.g. kinematics, equilibrium).

Example: Solve \( x^3 + 4x^2 + x - 6 = 0 \)

  1. From the main menu select Equation/Func (or press the corresponding shortcut key).
  2. Choose Polynomial.
  3. Select degree 3.
  4. Enter the coefficients in order: 1 (for \(x^3\)), 4 (for \(x^2\)), 1 (for \(x\)), −6 (constant term). Press EXE after each.
  5. Press EXE again to obtain the real roots.

Always write the polynomial and your algebraic method (or factorisation attempt) in the answer booklet. Use the calculator to verify, not to replace working.

Exam Technique: Converting Calculator Roots back into Factorised Form \((x - a)(x - b)\)

In IGCSE Mathematics, questions often explicitly ask you to "Factorise fully" or "Show your working". If you only write the final answers from your calculator, you will lose method marks. Here is how to use the calculator roots to quickly work backwards and write the correct factorised steps:

  1. Integer Roots (Whole Numbers):
    If the calculator gives integer roots like \( x = 2 \) and \( x = -3 \), flip the signs to form the brackets:
    \[ (x - 2)(x + 3) = 0 \]
  2. Fractional Roots (Crucial for Quadratic Expressions):
    If the calculator gives a fraction root like \( x = \frac{3}{2} \) (or 1.5, convert it to a fraction first):
    • Multiply by the denominator: \( 2x = 3 \)
    • Subtract the numerator: \( 2x - 3 = 0 \)
    • The bracket factor is \((2x - 3)\).
    Example: If the roots of a quadratic are \( x = \frac{3}{2} \) and \( x = -4 \), the fully factorised form is: \[ (2x - 3)(x + 4) = 0 \]

Pro Tip for Show-Your-Working Questions: First write down the factorised line \((2x - 3)(x + 4) = 0\) as your working step, then write the final answers \(x = \frac{3}{2}\) or \(x = -4\). This guarantees full method and accuracy marks!

5. Solving simultaneous equations

The same Equation/Func mode solves linear systems with up to four unknowns. Ideal for checking answers in coordinate geometry, circuit problems, or mixture questions.

Example: Solve \( 2x + y = 5 \) and \( -4x + 6y = 12 \)

  1. Open Equation/Func → Simul Equation.
  2. Select 2 unknowns.
  3. Enter coefficients row by row:
    • First equation: A = 2, B = 1, C = 5
    • Second equation: A = −4, B = 6, C = 12
  4. Press EXE to display \( x \) and \( y \).

Show elimination or substitution steps in your script. The calculator result is a check only.

6. Finding the factorisation (prime factors) of a number

Many ClassWiz models include a FACT (or prime-factorisation) function that decomposes a positive integer into primes. This is useful for simplifying fractions, finding LCM/HCF, or checking square-free parts of numbers under a square root.

Typical key sequence (fx-991EX / similar)

  1. Enter the positive integer (e.g. 360).
  2. Press SHIFT then the key that shows FACT (often above the degrees/minutes key or available via OPTN on some models).
  3. The display returns the prime factorisation, e.g. \( 2^3 \times 3^2 \times 5 \).

If your exact model does not show FACT on the keyboard, consult the quick-start guide or use repeated division by small primes and store intermediate results in memory. Knowing the manual method remains essential for non-calculator papers.

7. Using the SOLVE function for direct equations

Many scientific calculators (such as the Casio ClassWiz series) feature a numerical solver (SOLVE) that can directly compute an unknown variable $x$ in linear or algebraic equations without manually rearranging them first.

Example: Solve $2x = 3x + 2$ directly

  1. Enter the left side of the equation: type 2 then press ALPHA + ) to insert X.
  2. Insert the equals sign (=): press ALPHA + CALC (or the key marked = in red/pink above CALC). Do not use the standard = / EXE key.
  3. Enter the right side of the equation: type 3, press ALPHA + ) for X, then type + 2. The display will show 2X=3X+2.
  4. Solve the equation: press SHIFT + CALC (SOLVE).
  5. The calculator will prompt a starting value for $X$ (e.g., X=0). Press = or EXE to execute the calculation.
  6. The screen will display the result: X = -2 (along with L-R = 0 to indicate exact convergence).

Exam Tip: The SOLVE function uses numerical iteration to find solutions. While extremely useful for verifying answers or checking complicated algebraic steps in Physics and Maths, remember to show full algebraic working in your answer script to secure method marks.

8. Evaluating expressions using the CALC (Substitution) function

Instead of re-typing a long algebraic function multiple times when substituting different values, you can use the CALC key to evaluate expressions instantly. This is extremely efficient for verifying factorisations, checking substitution steps, or building tables of values for graphing.

Example: Evaluate \( 2x^2 - 3x + 5 \) for different values of \( x \)

  1. Type the algebraic expression onto the screen: type 2, press ALPHA + ) for X, press x², type - 3, press ALPHA + ) for X, then type + 5.
  2. Press the CALC key (located under the top-left screen area).
  3. The calculator will display X? asking for a value to substitute.
  4. Enter your chosen value (e.g., type 4) and press = or EXE. The calculator will output the result (21).
  5. To test another value (e.g., \( x = -2 \)), simply press CALC again, type -2, and press =.

Pro Tip for Checking Answers: If you expanded or simplified an expression in an exam question, type your expanded form and use CALC with a test number (e.g., \( x = 3 \)). Then type the original unexpanded question and test it with the same number. If both yield the exact same output, your algebraic expansion is correct!

9. Switching Between Degrees (D) and Radians (R)

One of the most common setup errors in IGCSE exams is calculating trigonometric functions in the wrong angle mode. Standard IGCSE Mathematics (0580/0980) and Physics (0625) require calculations in Degrees, while IGCSE Additional Mathematics (0606) often requires Radians for calculus and sector area problems.

How to Check and Switch Angle Modes

  1. Check the screen indicator: Look at the top of your calculator display. A small D indicates Degree mode, while R indicates Radian mode.
  2. Switching modes (Casio ClassWiz series):
    • Press SHIFT + MENU (SETUP).
    • Select Angle Unit (or press 2).
    • Choose 1 for Degree or 2 for Radian.
Critical Exam Warning: Always check your angle mode before starting a trigonometry question!
  • Evaluating \(\sin(30^\circ)\) in Degree mode yields 0.5 (Correct).
  • Evaluating \(\sin(30)\) in Radian mode yields -0.9880... (Incorrect for standard degree questions).

10. Other high-value functions for IGCSE

11. Exam-day checklist

12. Official Regulations & Exam Board Guidelines

Calculator requirements vary slightly by exam board and syllabus code. To ensure full compliance during your examinations, please refer to the official guidelines provided by the major examination boards:

Official Links & Documentation

Important: Resetting your calculator clears custom stored variables (A–F, X, Y, M). Re-verify your settings immediately after a reset.

Check your predicted grades after practice papers
Enter your raw component marks and see the weighted total and grade threshold instantly.

Open the free IGCSE Grade Calculator →

Frequently asked questions

Are graphical calculators allowed in Cambridge IGCSE Mathematics 0580?

No. Graphic display and CAS are prohibited. Use a scientific calculator such as the Casio fx-991EX / fx-991CW or fx-83GT CW.

What should I do if my calculator is accidentally set to Radians?

Press SHIFT then SETUP (or MENU), select Angle Unit, and choose Degree. Always check for a small "D" at the top of your screen before starting a trigonometry question.

Can I use a calculator with a Computer Algebra System (CAS)?

No. Built-in symbolic algebraic manipulation and symbolic differentiation/integration are explicitly banned under Cambridge regulations.

Is the Casio fx-991EX allowed?

Yes. It is a non-CAS scientific calculator and is one of the most commonly accepted models for IGCSE examinations worldwide.

Do I still need to show working if the calculator gives the answer?

Yes. Method marks are awarded for clear algebraic or numerical steps. An unsupported final answer usually scores zero for method.

What about Cambridge International Mathematics 0607?

That syllabus requires a graphic display calculator for Papers 3–6. The advice on this page focuses on the more common 0580/0980 and science subjects. Always read your own syllabus document.

Calculator regulations are set by the examination board and can be updated. Always verify the current Cambridge Handbook and your specific syllabus (and the front of the question paper) before the exam. This guide summarises publicly available rules as of 2026 and is provided for educational purposes only.

Other notes

Tools

Blogs

About the Developer

I am Chew, an education technology developer and academic consultant with 5+ years building educational websites. I developed the IGCSE Grade Calculator to bridge the gap between complex official PDF thresholds and student accessibility.

The mathematical models used in this calculator are verified against the Cambridge Assessment International Education (CAIE) guidelines for component weighting. This ensures that the “Total Weighted Mark” produced here matches the logic used by official examiners.