10 Calculator Tricks Every GCSE Maths Student Needs Before the Calculator Paper

The calculator paper is where a lot of students leave marks on the table, not because they cannot do the maths, but because they do it the slow way. Your Casio can factorise numbers, build tables of values, simplify fractions, convert units of time and remember long decimals for you. Learning ten buttons now will buy you back precious minutes in the exam and cut out a heap of copying errors. If you want to sharpen the other paper too, our guide to the non-calculator paper covers the mental tactics that matter there.

Everything below is written for the Casio fx-83GT X and fx-85GT X, which are the calculators most UK schools hand out. Other allowed models have the same features, though the button may sit in a slightly different place.

The ten tricks at a glance

#	Trick	Buttons (Casio Classwiz)	Typical exam question
1	Product of prime factors	number, =, SHIFT, FACT	”Write 550 as a product of its prime factors”
2	Table of values	MENU, 3	”Complete the table and draw the graph of y = 2x − 3”
3	Standard form both ways	×10ˣ and ENG	”Write 6 500 000 in standard form”
4	Simplify fractions	fraction key, =	“Write 90/160 in its simplest form”
5	Mixed and improper fractions	SHIFT, S⇔D	”Write 54/5 as a mixed number”
6	Decimal hours to h:m:s	° ’ ” key	Speed, distance and time
7	Digit separator	SHIFT, MENU, setup	Reading large answers correctly
8	Ratio in the form 1 : n	MENU, 4	”Write 90 : 40 in the form 1 : n”
9	Fraction after a long expression	) then fraction key	The quadratic formula
10	Store and recall a value	STO, then SHIFT, STO	Multi-step trigonometry and surds

1. Prime factors in one press

Type the number, press equals, then SHIFT and FACT. For 550 the screen shows 2 × 5² × 11, which is exactly the index form the mark scheme is looking for. Try it again on 360 or 1 000 so the button feels automatic. In a “find the highest common factor” question this alone can turn a five-minute factor tree into thirty seconds.

2. Tables of values for graphs

Graph-drawing questions almost always start with a table of x and y values. Press MENU then 3 to enter the table function. Type the equation, for example 2x − 3, using ALPHA and the x key (on most Casios this is printed above the close bracket). Press equals, skip the g(x) prompt with another equals, then set the start, end and step. A start of −2, an end of 2 and a step of 1 gives you all five coordinates instantly. Plot them, join them with a ruler, and the marks are yours.

Tip: The table function is also brilliant for checking iteration and trial-and-improvement questions. Set a small step such as 0.1 and you can watch the sign change happen.

3. Standard form in both directions

To turn standard form into an ordinary number, type 3.26, press the ×10ˣ key, type 9 and press equals. The calculator shows 3 260 000 000. Be warned that this does not expand negative powers, so 3.26 × 10⁻⁹ stays as it is.

Going the other way, type 6 500 000, press equals, then press ENG. You get 6.5 × 10⁶. The ENG button only uses powers that are multiples of three, so 650 000 shows as 650 × 10³. That is not proper standard form, but it gets you close, and shifting the decimal point twice more gives 6.5 × 10⁵. For a full refresher, see our post on standard form for GCSE Maths.

4. Simplify any fraction

Enter 90 over 160 with the fraction key and press equals. The calculator returns 9/16. It works for any fraction, and it is a quick way to check a probability or ratio answer you have worked out by hand.

5. Mixed numbers and improper fractions

Type 54/5 and press equals, then SHIFT and S⇔D. You get 10 and 4/5. To go the other way, press SHIFT and the fraction key to get the mixed-number template, enter 6 and 5/7, and press equals. The calculator converts it to 47/7 for you.

6. Decimal hours into hours and minutes

Speed, distance and time questions love to leave you with something like 6.55 hours. Type 6.55, press the degrees-minutes-seconds key (marked ° ’ ”) and then equals. The screen shows 6°33’0”, which reads as 6 hours 33 minutes. No more multiplying the decimal part by 60 and hoping you did not slip.

Remember: 6.55 hours is not 6 hours 55 minutes. Students lose this mark every single year. Let the calculator do the conversion.

7. Turn on the digit separator

Long answers such as 4 500 000 are easy to misread. Press SHIFT then MENU to open setup, scroll to the bottom, choose the digit separator option and switch it on. From then on large numbers are spaced into groups of three, which makes copying them onto the answer line far safer.

8. Ratios in the form 1 : n

Press MENU then 4 for the ratio mode and choose option 2 for the 1 : n layout. Enter 90 and 40 in the first ratio, put x where n belongs, and the calculator tells you that 90 : 40 is 1 : 4/9. You can leave it as a fraction or press S⇔D to see the decimal, depending on what the question asks for.

9. Add a fraction without retyping everything

Picture this: you are halfway through the quadratic formula, you have typed −3 + √(64 + 20), and only then remember it all needs to go over 2. Pressing the fraction key now would only grab the square root. Instead, type a close bracket, then press the fraction key. Everything back to the matching bracket jumps into the numerator. Delete the stray bracket, type 2 underneath, and you are done. This is a genuine time-saver on every quadratic equation that will not factorise.

10. Store a number and recall it later

Suppose a question needs the cube root of 65 multiplied by tan 60°, and then wants you to square that result and add it to itself two lines later. Writing out a twelve-digit decimal invites rounding errors. Instead, calculate the value, press STO (just above the 7 on most Casios) and then a letter key such as A. Press equals and the number is saved. Later, type ALPHA A, square it, add ALPHA A again, and the calculator uses the full-precision value.

Press SHIFT and STO to open RECALL and see everything you have saved.

Did you know? Rounding a value part-way through a question and then using it again is one of the most common reasons students drop accuracy marks in Higher trigonometry. Storing the value keeps every decimal place intact.

Clear the memory before you walk in

Stored values and history can be treated as unauthorised material, and invigilators may ask you to prove the calculator is clean. Press SHIFT then RESET (the 9 key on the Classwiz), choose option 2 for Memory and press equals to confirm. Open RECALL again and every letter should read zero. Add this to your exam-day checklist alongside spare batteries and a ruler.

Put the tricks into practice before exam day

Knowing a button exists is not the same as reaching for it under pressure. Spend a week using these shortcuts on real questions until they are second nature. Every one of the topics above sits inside our revision apps, so you can drill them with your calculator beside you.

• GCSE Maths is the complete GCSE Maths revision app, with Number, Algebra, Geometry and Statistics in a single bundle. It is the best pick if you want to rehearse every trick in one place.
• GCSE Number covers place value, fractions, percentages, ratio, powers, roots and rounding, so it is ideal for tricks 1, 3, 4, 5 and 8.
• GCSE Algebra takes you through expressions, equations, inequalities, sequences and graphs, where the table function and the quadratic formula shortcut earn their keep.
• GCSE Geometry gives you visual practice with 2D and 3D shapes, angles, trigonometry, transformations and circle theorems, the perfect home for the store-and-recall trick.
• GCSE Statistics covers surveys, sampling, charts, averages, spread and probability theory, where fraction simplification and stored totals save real time.

Across the four subject apps you get 2900+ questions, all written for Foundation and Higher tier. Work through a topic, grab your calculator, and see how many seconds each of these ten tricks saves you. Those seconds add up to whole questions by the end of the paper.