Casio fx-991ES PLUS Scientific Calculator – Free Online Emulator

This free online scientific calculator emulates the Casio fx-991ES PLUS, the world's most popular scientific calculator. It supports 403 built-in functions and 10 calculation modes including COMP, STAT, BASE-N, MATRIX, VECTOR, TABLE, EQN, CMPLX, and VERIF.

Key Features

• Complex number arithmetic in rectangular (a+bi) and polar (r∠θ) form
• Matrix operations: addition, subtraction, multiplication, determinant, inverse, transpose (up to 3×3)
• Vector calculations: dot product, cross product, absolute value (up to 3D)
• Numerical definite integration ∫(f(x),a,b) with user-defined limits
• Numerical differentiation d/dx(f(x),a)
• Summation Σ(f(x),start,end)
• Arbitrary nth root — type any root order
• Equation solver: linear, quadratic, cubic, and simultaneous (2–3 variables)
• Statistical regression: 1-VAR, LinearReg, QuadReg, LogReg, ExpReg, PwrReg, InvReg
• Normal distribution functions P(t), Q(t), R(t)
• Base-N arithmetic: binary, octal, decimal, hexadecimal with AND, OR, XOR, XNOR, NOT
• Table mode: evaluate a function over a range with a fixed step
• Fraction and mixed-number display and input
• Prime factorisation (FACT)
• GCD, LCM, Int (truncate), Intg (floor) functions
• Multi-statement expressions using colon separator
• Full keyboard input with arrow-key cursor navigation
• Degree, radian, and gradian angle modes with DRG conversion
• Natural textbook display — fractions, exponents, and roots shown as written

Frequently Asked Questions

Is this calculator free?

Yes. Completely free, no account or install required. Works in any modern browser.

Can I use it offline?

Once loaded, all calculations run locally in your browser with no internet needed. Install it to your home screen as a PWA for full offline access.

Does it support keyboard input?

Yes. Numbers, operators, Enter (=), Backspace (delete), Escape (AC), and arrow keys all work from the keyboard.

What is the Casio fx-991ES PLUS?

The Casio fx-991ES PLUS is a non-programmable scientific calculator with a natural textbook display that shows fractions, roots, and integrals as they appear in textbooks. It is widely used in schools and universities around the world and supports 403 functions.