Maths / Calculate
Casio fx-991ES PLUS Alternative: Free Online Scientific Calculator
Practise scientific calculations, equations and statistics with the fx-991ES PLUS key layout.
Casio fx-991ES PLUS Alternative: Free Online Scientific Calculator: The Natural Display key layout puts a fraction key, a square-root key and a power key in the six-column scientific block. MODE has COMP, CMPLX, STAT, BASE-N, EQN, MATRIX, TABLE and VECTOR, numbered 1 through 8. The supplied fx-991ES PLUS guide does not list a DIST mode. SHIFT MODE opens SETUP; select Deg or Rad before using trigonometry. Fractions use the division key and show a stacked result in this browser version and S⇔D changes the result between fraction and decimal. Press MODE → 5 → Quadratic to open the coefficient table. Enter 1, −5 and 6 for x²−5x+6; Calculate gives roots 3 and 2. Choose 2 unknowns to enter each equation as coefficients followed by its right-hand side. For 2x+y=5 and x−y=1, use rows 2,1,5 and 1,−1,1: x=2 and y=1. MODE → 3 opens the observation table. Enter 2,4,4,4,5,5,7,9 to see population σx=2 and sample sx=2.138089935. Press CALC to substitute x into an expression, or SHIFT CALC to solve from a starting value. The integral key opens fields for the function and bounds, and its SHIFT function opens a derivative calculation. The REPLAY cross sits between the left and right function keys. The key map lists primary, SHIFT and ALPHA legends so you can find familiar functions. Constants and conversions are restricted to a documented subset. Some complex-mode key remappings are not supported. Use this as a calculation and study aid, and check important answers against your course conventions. Runs 100% locally in your browser with zero server file uploads.
- Category
- School & study tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
CASIO and the model names fx-991ES PLUS and fx-991MS are trademarks of CASIO Computer Co., Ltd. TOEA is not affiliated with or endorsed by CASIO. This independent calculator does not run CASIO software.
Model guide
CASIO’s fx-570ES PLUS/fx-991ES PLUS user’s guide (https://support.casio.com/en/manual/manual.php?cid=004) documents the model’s modes, key functions and worked examples. Choose your model in the manual catalogue.
Constants and conversions
NIST CODATA 2018 (https://physics.nist.gov/cuu/Constants/) supplies the scientific constant subset. NIST SP 811 (https://www.nist.gov/pml/special-publication-811) supplies the supported unit conversion factors. Only the cited subset is exposed.
How to use it
- Choose a mode with MODE.
- Enter a calculation in the display or use the keypad.
- Open EQN or the statistics mode for a coefficient or observation table.
Privacy & limitations
Calculations and saved state stay in this browser. Nothing is uploaded.
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Frequently asked questions
Is this a CASIO calculator?
CASIO and the fx-991 model names are trademarks of CASIO Computer Co., Ltd. TOEA is not affiliated with or endorsed by CASIO. This independent calculator does not run CASIO software.
Can I use this on an exam?
This page is for study and practice. Proctored exams generally prohibit online calculators. Check your exam’s permitted devices before attending.
Does it include every device function?
No. The key positions are familiar, but the browser version has simplified workflows and a smaller supported function set. The panel beside the body describes the main limitations.
Free tool · runs in your browser · no account required