Exam day, rules & kit
Which calculator do I need for GCSE maths?
For GCSE maths, the standard choice is the Casio fx-83GT CW (or the fx-85GT CW - the same calculator with solar backup). It does everything the exams need. The fx-991CW costs a little more and is worth it if you take triple science or expect to carry maths on to A-level. All three are allowed in GCSE exams. Buy early and use the same model for all your practice.
Last updated 29 July 2026 · Written and fact-checked by the GCSEwiz team
The three realistic options
Almost every UK maths classroom standardises on Casio's GT/Classwiz range, which keeps the choice simple:
| Model | Rough price | Who it suits |
|---|---|---|
| Casio fx-83GT CW | £12–£17 | The GCSE standard - everything the exam needs |
| Casio fx-85GT CW | £14–£20 | Identical, plus solar backup - worth £2 for the battery peace of mind |
| Casio fx-991CW | £25–£35 | A big step up - equation solving, better for triple science and future A-level maths |
What the exam rules allow
Calculators are allowed on most GCSE maths papers (each board runs one non-calculator paper - check which of your papers is which). The JCQ rules say a calculator must not communicate, must not store or retrieve text or formulae, and must not do symbolic algebra - every model above is comfortably within the rules. Cases and lids stay outside, and you are responsible for clearing anything stored in memory. Graphical calculators are technically permitted at GCSE but are expensive overkill; nothing on the paper needs one.
Is the fx-991CW worth the upgrade?
If GCSE maths is the end of the road for you, no - the fx-83GT CW leaves nothing on the table. Say yes to the upgrade if you take triple science (it handles the physics number-crunching more gracefully), or if there is any chance you continue maths after GCSE: the 991 is the assumed baseline at A-level, and buying it once at 15 beats buying twice. The one caution: its extra menus take a little learning, which is exactly why the next section matters.
The rule that matters more than the model
Whatever you buy, buy it now and practise on it. Marks are lost every summer by students meeting an unfamiliar calculator in the exam - fumbling for the fraction button or misreading the display under time pressure. The calculator you sit the exam with should be the one your fingers already know from months of practice. Borrowing a different model the night before is a small self-sabotage.