Comparison

Scientific Calculator Plus 991 vs Sentry

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

Head to head
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
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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

About

Sentry

Features
Read full description

An application helping to book and access study spaces, rooms, resources eg computers consistent with academia facilities. If configured, it allows users to present their ID card barcode on their phone.

Screenshots

Scientific Calculator Plus 9914 screens
Sentry4 screens

Verdict

The call

The clearest difference is in-app purchases: Sentry at none against Scientific Calculator Plus 991's 4. Sentry also leads on ads (none vs shown) and iOS requirement (13.0 vs 15). Scientific Calculator Plus 991's advantage is update cadence (fortnightly vs every 19 months) and device support (4 vs 2). On price 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

Both are free to download. Scientific Calculator Plus 991 sells 4 in-app purchases, starting at $1.99 per month. Sentry asks for nothing beyond the download.

UpkeepUpdate frequency

Scientific Calculator Plus 991 ships an update fortnightly, Sentry every 19 months. Both last shipped on October 27, 2026.

Scorecard5 real differences · 5 level
Scientific Calculator Plus 991 versus Sentry: the parameters behind the verdict, then further details
ParameterScientific Calculator Plus 991Sentry
PriceFreeFree
Rating4.7 (13K ratings) — better—
Positive reviews91.7% of reviews—
Number of ratings13K — better—
Update frequencyFortnightly — betterEvery 19 months
AdsYesNo — better
In-app purchasesYesNo — better
MonetizationFree with in-app purchases—
DevicesiPhone, iPad, iPod, Mac — betteriPhone, iPod
Requires iOS1513.0 — better
Further details — not scored
Size169 MB28 MB
Age rating12+4+
DeveloperTran DuyS. B. ELECTRONIC SYSTEMS LIMITED

Bugs and requests

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

Sentry

Not enough reviews yet to summarise bugs or requests.

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
None

Sentry

No in-app purchases

Questions

Is Scientific Calculator Plus 991 free?
Scientific Calculator Plus 991 is free to download, with in-app purchases available.
Is Sentry free?
Sentry is free to download, with no in-app purchases.
Do Scientific Calculator Plus 991 or Sentry have ads?
Scientific Calculator Plus 991 shows ads; Sentry does not.
Which is updated more often, Scientific Calculator Plus 991 or Sentry?
Scientific Calculator Plus 991 ships an update fortnightly, and Sentry every 19 months. Most recently, Scientific Calculator Plus 991 was updated on October 27, 2026 and Sentry on October 27, 2026.

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