Scientific calculator plus 991

What it is

Scientific calculator plus 991 is a mobile calculator for students who need more than basic arithmetic. It brings together familiar scientific-calculator layouts with tools for algebra, equations, graphing, calculus, formulas, constants and unit conversions. It is aimed at secondary-school and university students, especially those studying mathematics, physics, engineering or other STEM subjects.

What it does well

• Several calculator styles: simulated layouts based on popular 300 Plus, 115 Plus and 991-series calculators can make the controls easier to recognise.
• Equation solving: supports quadratic and cubic equations, as well as systems of equations.
• Graphing: handles polar, parametric and implicit functions, with tools for examining roots, tangents and derivatives.
• Symbolic work: its computer algebra features are designed for algebraic manipulation, not only numerical answers.
• Reference tools: built-in mathematical and physics formulas, constants and unit conversions reduce the need to switch between apps.

What to watch for

The interface follows the dense, button-heavy design of a physical scientific calculator rather than a minimal phone app. That can be useful if you already know these calculator layouts, but the number of functions may take time to learn and can feel crowded on smaller screens. Its advanced tools are most useful when you already understand the underlying maths; it is a calculator and study aid, not a replacement for learning the methods.

Reach and fit

With a 4.86 rating from more than 533,000 reviews and 50,000,000+ installs, the app has broad use among Android learners. It is published by Tools for student in the Education category. Choose it if you want one calculator app for everyday scientific calculations and more demanding school or university problem-solving.