01P(X ≥ 3)
Probability & distributions
Normal and binomial probabilities, cumulative distributions and inverse normal calculations.
Pocket 991FOR A-LEVEL MATHS & FURTHER MATHS
Your calculator.
More familiar.
More useful.
Practise the A-level calculator you use in class, on your phone or in your browser. Pocket 991 brings familiar 991 EX, 991 CW and CG50-style workflows together with built-in, step-by-step tutorials.
Try all three calculators and their tutorials free in your browser. The iPhone and iPad app is a one-off paid download; existing owners receive updates free.
● LIVE CALCULATORFull screen ↗
Choose 991 EX, 991 CW or CG50, then tap HELP for a worked guide. Your keyboard works here too.
MORE THAN THE FOUR OPERATIONS
There’s a lot hiding
behind those keys.
Get more from the scientific calculator you already own. Practise the features that come up in A-level Maths and Further Maths, then use those skills on your physical calculator.
02ax² + bx + c = 0
Equations & inequalities
Work with polynomial roots, simultaneous equations and numerical solving.
03MatA + MatB
Matrices & vectors
Define your values, then explore addition, multiplication and determinants.
04a + bi
Complex numbers
Practise complex arithmetic and work with rectangular and polar representations.
05y = a + bx
Statistics & regression
Enter data, find summary statistics and calculate a line of best fit.
06y = x² − 4
Graphs, tables & calculus
Plot functions, trace curves, find roots, turning points and intersections, and explore tables, derivatives and definite integrals.
FOR STUDENTS. AND THE PEOPLE TEACHING THEM.
Show the keys.
Share the understanding.
Practise between lessons
Open Pocket 991 on your phone or in your browser, try a worked example and learn where the useful features live. Follow the highlighted keys or take over as soon as you’re ready.
Put your calculator on their screen
Teaching online? Open Pocket 991 in your browser and share your screen through your usual lesson platform. Show students exactly which keys you press and how the display changes, without holding a calculator up to a webcam.
Open for a lesson ↗LEARN BY PRESSING THE KEYS
From “which button?”
to “I’ve got it.”
Find your feature
Press HELP. Search for an operation or browse the tutorial library.
Follow the light
Press each highlighted key and see the calculation change on the actual display.
Make it yours
Tap Take over at any point. Keep the current calculation and try your own numbers.
A few useful things to know.
Is the browser calculator free?
Yes. All three browser calculators and their built-in tutorials are free to use. The iPhone and iPad app is a one-off paid download with the tutorials included. Existing owners receive app updates free, and there is no tutorial subscription or unlock fee.
Which calculators can I practise?
Here in the browser, you can use independent 991 EX- and 991 CW-style scientific calculators, plus a CG50-style graphing calculator. The CG50 covers calculation, graphs, tables, equations, statistics and distributions, matrices and selected Dynamic, Conic, Recursion and 3D workflows, with 234 worked tutorials. Some specialist modes and physical-calculator details remain partial. Check the App Store listing for the currently available iOS version.
Can I use it in an exam?
This is a practice tool for your phone, tablet or browser. Use the physical calculator permitted by your exam centre in the exam itself.
Does the website have Apple Intelligence?
The web calculator includes local tutorial search and built-in guides. Apple’s on-device language model is available only in the native app on compatible devices. The website does not send your questions to a paid AI service.
Is it exactly the same as a physical calculator?
Pocket 991 is an independent learning and practice tool for familiar scientific- and graphing-calculator workflows. It is not made by or affiliated with Casio. Some behaviour, specialist modes and numerical precision differ from physical calculators, so use it alongside your calculator. It performs numerical calculus rather than general symbolic algebra.
Where can I get the app?
The iPhone and iPad app is on the App Store. The App Store listing shows the currently approved version and price. You can also try all three calculators here in your browser.