Comparison

Probability vs Scientific Calculator Plus 991

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

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.

Highlights
  • Compute probabilities
  • Determine percentiles
  • Plot probability density function
  • Plot probability mass function
  • Supports 10+ continuous distributions
  • Supports 5+ discrete distributions
Features
Read full description

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.

About

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.

Highlights
  • Natural display input
  • Graphing module
  • Formula library
  • Unit and currency converter
  • Algebra and calculus tools
  • Matrix and vector operations
  • Statistical calculations
Features
Read full description

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

Probability4 screens
Scientific Calculator Plus 9914 screens

Verdict

The call

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

CostPrice · In-app purchases · Ads · Monetization

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.

ReceptionRating · Positive reviews · Number of ratings

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.

UpkeepUpdate frequency

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.

Scorecard9 real differences · 1 level
Probability versus Scientific Calculator Plus 991: the parameters behind the verdict, then further details
ParameterProbabilityScientific Calculator Plus 991
Price$1.99Free — better
Rating4.9 (193 ratings) — better4.7 (13K ratings)
Positive reviews97.2% of reviews — better91.7% of reviews
Number of ratings19313K — better
Update frequencyEvery 3 monthsFortnightly — better
AdsNo — betterYes
In-app purchasesNo — betterYes
MonetizationFree — betterFree with in-app purchases
DevicesiPhoneiPhone, iPad, iPod, Mac — better
Requires iOS26.015 — better
Further details — not scored
Size7 MB169 MB
Age rating17+12+
DeveloperMatthew BognarTran Duy

Customer experience

Probability

All ratings193 ratings
Positive96.9%
Neutral1.0%
Negative2.1%
Written reviews71 reviews
Positive97.2%
Neutral1.4%
Negative1.4%

Scientific Calculator Plus 991

All ratings12,520 ratings
Positive92.0%
Neutral2.6%
Negative5.4%
Written reviews509 reviews
Positive91.7%
Neutral3.1%
Negative5.1%

User reviews

Probability

From 193 App Store ratings

What 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 ratings

What 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
Show 2 more
  • 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

None

Probability

No in-app purchases

4 purchases

Scientific Calculator Plus 991

Subscriptions2
  • Calculator month subscription$1.991 Month
  • Calculator yearly subscription$3.991 Year
One-time2
  • Calculator Premium$5.99
  • Calculator Pro$5.99

Questions

Is Probability free?
Probability costs $1.99, with no in-app purchases.
Is Scientific Calculator Plus 991 free?
Scientific Calculator Plus 991 is free to download, with in-app purchases available.
Which has better reviews, Probability or Scientific Calculator Plus 991?
Probability is rated higher. Probability averages 4.9 out of 5 from 193 ratings, while Scientific Calculator Plus 991 averages 4.7 from 13K ratings.
Do Probability or Scientific Calculator Plus 991 have ads?
Scientific Calculator Plus 991 shows ads; Probability does not.
Which is updated more often, Probability or Scientific Calculator Plus 991?
Probability ships an update every 3 months, and Scientific Calculator Plus 991 fortnightly. Most recently, Probability was updated on November 6, 2026 and Scientific Calculator Plus 991 on November 9, 2026.

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