Probability vs Scientific Calculator Plus 991
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Probability
Calculate probabilities, find percentiles, and visualize probability density or mass functions for a wide range of continuous and discrete statistical distributions. Explore common distributions like normal, binomial, Poisson, and many more.
- Compute probabilities
- Determine percentiles
- Plot probability density function
- Plot probability mass function
- Supports 10+ continuous distributions
- Supports 5+ discrete distributions
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Replace your statistical tables with an interactive, graphical app! Compute probabilities & percentiles, and plot the probability density/mass function for the Beta, Chi-Square, Exponential, F, Gamma, Gumbel, Logistic, Lognormal, Normal, Pareto, t, Triangular, Uniform, Weibull, Binomial, Geometric (2 versions), Hypergeometric, Negative Binomial (2 versions), and Poisson distributions. Now supports Español.
Scientific Calculator Plus 991
This app is a powerful scientific calculator with graphing capabilities, a formula library, and a unit converter. It offers natural display input, advanced math functions for algebra, calculus, and statistics, and supports various number bases and formats.
- Natural display input
- Graphing module
- Formula library
- Unit and currency converter
- Algebra and calculus tools
- Matrix and vector operations
- Statistical calculations
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NCalc — Powerful Scientific Calculator, Graphing, and Converter NCalc combines a natural-display scientific calculator, advanced math tools, a full graphing module (as 83/84 calculator), a large formula library, and a comprehensive unit and currency converter—designed for students, engineers, and anyone who loves math. ◉ Main Calculator Features - Natural display: Enter expressions exactly as in textbooks—fractions, roots, exponents, and more—see results as written on paper. - Keyboard layout: Matches popular models for familiarity and speed: 115 ES Plus, 991 ES Plus, 300 ES Plus, and 991 EX. - Symbolic and numeric modes: Perform exact fraction calculation or evaluate numerically when needed. - Arbitrary precision integers: Work with very large integers without losing accuracy. - Output types: Choose from fraction, mixed fraction, decimal, repeating decimal, degrees/minutes/seconds, and polar coordinates. - Angle units: Degree, radian, and gradian (grade). - Decimal formatter: Display numbers in normal, engineering, engineering SI, scientific, or fixed formats. - Calculation history: Review and reuse past calculations with ease. - Copy and paste support for fast data entry and sharing. ◉ Algebra, Calculus, and Core Math - Algebra calculation: Expansion, factorization, simplification, and more. - Calculus calculator: Derivatives, integrals, and limits of expressions. - Complex number calculation: Arithmetic, polar/rectangular conversion, exponential, logarithm, powers, roots, and full trigonometric functions. ◉ Equations and Inequalities - Equation solver: Solve general equations, plus dedicated solvers for quadratic, cubic, and quartic equations. - System of equations solver: Solve systems with 2, 3, or 4 variables. - Inequality solvers: Quadratic, cubic, and quartic inequalities with interval-based solutions. ◉ Matrices and Vectors - Operations: Addition, subtraction, multiplication for matrices and vectors. - Advanced tools: Determinant, inverse, transpose, rank, eigenvalues, and eigenvectors. ◉ Statistics and Distributions - Statistical calculation: Descriptive stats and regression calculation (including a regression plotter). - Distribution calculation: Normal distribution, binomial distribution, Poisson distribution, t-distribution, chi-square distribution, and F-distribution. ◉ Number Bases and Formats - Base N calculation: Effortlessly switch between binary, octal, decimal, and hexadecimal, with arithmetic in each base. ◉ Tables, Variables, and Custom Functions - Table Generator: Generate value tables based on any expression and range. - Calculator variables: Store values and reuse them across calculations. - User-defined functions: Create your own functions to streamline repetitive work. - Built-in constants: A rich set of mathematical and physical constants. ◉ Formulas - Extensive formula collection: Math and Physics formulas, clearly categorized—ideal for secondary school, high school, and university students. ◉ Unit Converter - Currency Converter - 1000+ unit conversions ◉ Graphing as 83, 84 calculator - Cartesian functions, implicit plots, polar, and parametric. - Tracing, roots, intersections, extrema, derivative, and integral evaluations on graphs. ◉ Auto-renewing subscription You may purchase an auto-renewing subscription through an In-App Purchase. • Auto-renewable subscription • Your subscription will be charged to your AppStore account at confirmation of purchase and will automatically renew (at the duration selected) unless auto-renew is turned off at least 24 hours before the end of the current period. • Current subscription may not be cancelled during the active subscription period; however, you can manage your subscription and/or turn off auto-renewal by visiting your AppStore Account Settings after purchase • Privacy policy and terms of use: https://ncalc-app.web.app/terms-of-services.html
Screenshots
Verdict
The clearest difference is price: Scientific Calculator Plus 991 at Free against Probability's $1.99. Scientific Calculator Plus 991 also leads on update cadence (fortnightly vs every 3 months) and ratings volume (13K vs 193). Probability's advantage is in-app purchases (none vs 4) and ads (none vs shown). On review sentiment there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Scientific Calculator Plus 991 is free to download; Probability costs $1.99 up front. Scientific Calculator Plus 991 sells 4 in-app purchases, starting at $1.99 per month. Probability asks for nothing beyond the download.
Probability holds the better App Store score, 4.9 against 4.7. That said, the two scores are not equally well evidenced: Scientific Calculator Plus 991 has 13K ratings behind it against 193, so its average is the more settled of the two. Written reviews point the same way: 97% of Probability's written reviews are positive against 92% of Scientific Calculator Plus 991's.
Probability ships an update every 3 months, Scientific Calculator Plus 991 fortnightly. The most recent releases landed on November 6, 2026 and November 9, 2026 respectively.
| Parameter | Probability | Scientific Calculator Plus 991 |
|---|---|---|
| Price | $1.99 | Free — better |
| Rating | 4.9 (193 ratings) — better | 4.7 (13K ratings) |
| Positive reviews | 97.2% of reviews — better | 91.7% of reviews |
| Number of ratings | 193 | 13K — better |
| Update frequency | Every 3 months | Fortnightly — better |
| Ads | No — better | Yes |
| In-app purchases | No — better | Yes |
| Monetization | Free — better | Free with in-app purchases |
| Devices | iPhone | iPhone, iPad, iPod, Mac — better |
| Requires iOS | 26.0 | 15 — better |
| Further details — not scored | ||
| Size | 7 MB | 169 MB |
| Age rating | 17+ | 12+ |
| Developer | Matthew Bognar | Tran Duy |
Customer experience
Probability
Scientific Calculator Plus 991
User reviews
Probability
From 193 App Store ratingsWhat we love
- 👍 Easy to use interface
- 📊 Great for probability distributions
- 💡 Useful for checking work and homework
- 💰 Free advanced functions
- 📈 Visualizes data and distributions
Room to improve
- 🚫 Not allowed on some exams
- 🤔 Some users want more features
Scientific Calculator Plus 991
From 13K App Store ratingsWhat we love
- 👍 Intuitive and easy to use
- 🚀 Powerful and feature-rich
- 💡 Customizable interface and settings
- 🔍 Extensive library of formulas and equations
- ⚙️ Handles complex math and scientific functions well
Room to improve
- 🐛 Occasional bugs and input issues
- 🔀 Confusing layout and button placement
- 💰 Some advanced features locked behind paywall
Bugs and requests
Probability
Requested features
7 requests- Exam mode similar to Geogebra
- Poisson distribution
- Allow setting plot boundaries (e.g., for Beta distribution)
- Make formulae available in offline mode
- Clearly introduce parameters
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- Add options after graph rendering (area above, between, outside values)
- Consistent terms for df across distributions
Scientific Calculator Plus 991
Reported bugs
3 issues- Keyboard input stops working after switching screens
- Incorrect calculation results for certain operations
- App crashes on some devices after recent update
Requested features
5 requests- Add option to change display font and color
- Improve cursor control and editing capabilities
- Implement auto-simplification for complex expressions
- Add more handwriting font options
- Expand graphing and equation solving features
In-app purchases
Probability
No in-app purchases
Scientific Calculator Plus 991
- Calculator month subscription$1.991 Month
- Calculator yearly subscription$3.991 Year
- Calculator Premium$5.99
- Calculator Pro$5.99
Questions
Is Probability free?
Is Scientific Calculator Plus 991 free?
Which has better reviews, Probability or Scientific Calculator Plus 991?
Do Probability or Scientific Calculator Plus 991 have ads?
Which is updated more often, Probability or Scientific Calculator Plus 991?
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