Casio fx-991EX Alternative: Free Online Scientific Calculator

Student tasks on the EX keypad

Distributions: MENU → Distribution offers Normal PD, Normal CD, Inverse Normal, Binomial PD/CD and Poisson PD/CD. For discrete distributions choose Variable or List; List accepts up to 45 comma-separated x values and returns a result for each.

Inequality: MENU → Inequality → Inequality, select degree 2, 3 or 4 and a relation (> 0, < 0, ≥ 0 or ≤ 0), then fill the coefficient grid. For x²−5x+6 > 0 the result is x<2, 3<x.

Fraction to decimal: enter 1 ÷ 2 + 1 ÷ 3, press = to see 5/6, then S⇔D to see 0.8333333333. SHIFT then S⇔D changes improper and mixed fractions.

Degrees: SHIFT → MENU (SETUP) → Angle Unit → Degree. Enter sin(30), then =, to obtain 1/2.

Statistics: MENU → Statistics. Enter each value and press =. OPTN → One-variable results shows n, mean, sums, standard deviations, quartiles and extrema. For regression, enter each x y pair in the entry line, then OPTN → Linear regression for y = a + bx. OPTN → ŷ estimates y from x; x̂ estimates x from y using the current regression.

Combinations: 5 → SHIFT → ÷ (nCr) → 2 → = gives 10. The closing parenthesis is supplied when evaluating an unfinished function call.

Quadratic: MENU → Equation → Quadratic, then enter a = 1, b = −5 and c = 6, pressing = after each. Read roots 2 and 3 and vertex (2.5, −0.25). For 2x+y=5 and x−y=1 choose Simultaneous equations and fill the two grid rows with 2, 1, 5 and 1, −1, 1, then Execute.

SOLVE: SHIFT → CALC, enter x²=2, press =, enter initial x = 1, then =. The root is 1.414213562 and the rounded L−R residual is 0.

Integration: ∫ → x² → = → 0 → = → 1 → = gives 1/3. SHIFT → ∫ opens derivative; SHIFT → x opens summation.

Matrix inverse: MENU → Matrix → Matrix inverse. Choose two rows and two columns, fill the grid with 1, 2, 3 and 4, then Execute. Arrow keys move between cells; Enter advances or calculates at the last cell.

Base conversion: MENU → Base-N → Base conversion, enter 255, then = to obtain FF. Hex AND takes two hexadecimal integers.

Normal distribution: MENU → Distribution → Normal CD. Enter lower −1, upper 1, standard deviation 1 and mean 0. The probability is 0.6826894921.

What is not supported

Spreadsheet, Verify, QR-code generation, device contrast and power control are unavailable. This is a simplified app interface: the app menus are simplified and the complete 47-constant catalogue is not provided. Only the displayed constants and conversions are provided. Input/output settings do not reproduce every physical display rule.

Key layout and operation

CASIO fx-570EX/fx-991EX User's Guide (edu.casio.com) supplies the functional key names and operation sequences. It describes QR as a QR-code function; quotient and remainder is a separate function in this independent calculator. The manufacturer's text and images are not reproduced on this page.

Constants and unit conversions

The displayed subset uses CODATA 2018 recommended SI values: c₀, h, e, k, Nₐ, G, electron mass and proton mass. NIST SP 811 Appendix B supplies the exact inch, foot, mile, pound and US liquid gallon conversion factors. These references distinguish exact definitions from measured constants.

Statistical calculations

NIST/SEMATECH e-Handbook of Statistical Methods documents the normal and binomial distributions, descriptive statistics and least-squares regression. Normal CD is an interval area, while binomial PD is a probability of an exact count.

How to use it

1. Enter an expression with the keypad, then press =. SHIFT and ALPHA each change the next key.
2. Press MENU and choose an app by its displayed number. OPTN opens calculations for that app.
3. Use S⇔D to switch between exact and decimal results, or SHIFT then MENU to change settings.

Privacy & limitations

Calculations and saved state stay in your browser. Reset calculator clears this page's saved working.