# CalcX9 > CalcX9 (iPhone/iPad app by Sim Ayers.) - Source: https://appshunter.io/ios/app/calcx9/id6765501365 (this page in markdown: same URL + `.md`) - Developer: [Sim Ayers](https://appshunter.io/developer/689788842) - Category: Education, Business - Price: $2.99 - Age rating: 4+ - Requires: iOS 26.0 · 8 MB - Languages: American English - Released: 2026-05-01 - Data updated: 2026-06-06 - User reviews in markdown: https://appshunter.io/ios/app/calcx9/id6765501365/reviews.md ## What is CalcX9? RPN CalcX9 This Calculator is a Reverse Polish Notation (RPN) calculator, typically an engineering or financial calculator that uses postfix notation. However, this calculator is designed for geometry and trigonometry students. It also includes standard mathematical functions and basic arithmetic operations. The RPN input method allows quick, efficient calculations without parentheses, making it ideal for on-site use where speed and accuracy are important. Example calculations and instructions for using the various functions of the Calculator are provided below. The calculations are pushed on to the stack for easy viewing. Up to 100 values can be added to the stack. The top of the stack is thr row just above the top buttons. The bottom of the stack is at the top of the screen, or it scrolls off the view of the stack. You can also scroll up the stack to see previous calculations and results. The stack stores the last 100 numbers entered or calculated, allowing you to easily reference and reuse them in future calculations. Select a number on the stack, and it will be copied to the input area, allowing you to use it in a new calculation. Do a long press on the stack and all of the information on the stack will be copied to the clipboard. Turn the animations on or off in the settings display. Click the gear icon in the top right corner to display the animation setting. You can also, select "User Selection", then upload your own image to use for the animation. It will automatically remove the background from the image, and set the back ground of the image to a transparent PNG file. CalcX9 has a 16 built-in calculators for: Quadratic-> calculates the Quadratic Equation from the three parameters a, b, and c Parabolic-> calculates the and plots the parabolic curve from the three parameters a, b, and c Law Sines-> calculates the sides and angles of a triangle from the three parameters a, b, and c, or Angle A, Angle B, and Angle C Law Cosines-> calculates the sides and angles of a triangle from the three parameters a, b, and c, or Angle A, Angle B, and Angle C Triangle-> calculates the 3 sides and 3 angles of an right triangle, given any two parameters Ellipse Cone-> calculates and plots the elliptical curve from the given parameters Hyperbola Cone-> calculates and plots the hyperbolic curve from the given parameters Parabola Cone-> calculates and plots the parabolic curve from the given parameters Pyramid-> calculates the pyramid side angles and lengths from the given parameters Cylinder-> calculates the helical curve and length from the given parameters Prism-> calculates the volume from the given parameters Trapezoid-> calculates the volume from the given parameters Circle-> calculates the helical curve and length from the given parameters Cone-> calculates the helical curve and length for the cone from the given parameters Sphere-> calculates the curve and length from the given parameters Unit Circle-> calculates the cosine, sine, tan from the given parameters Snd function button for sin, cos, tan -> for asin, acos, atan functions Buttons: x² -> number squared √2 -> square root of number 1/X -> 1 / number +/- -> plus or minus value π -> prints the number for pie φ -> prints the golden ratio of phi For RPN Usage: Enter a number, then press the enter key several times, each time you press the enter key the number will be added to the stack. Then press the + key to add the numbers together. Or use the - key to subtract, the * key to multiply, and the / key to divide. The calculator will always operate on the top two numbers on the stack. For example, to add 3, 4, and 5 together: Enter 3, then press the enter key (3 is now on the stack) Enter 4, then press the enter key (4 is now on the stack above 3) Enter 5, then press the enter key (5 is now on the stack above 4) Now press the + key (5 and 4 are added together to make 9, which is now on the stack above 3) ## Version history (last 3 releases) ### 1.2 — 2026-05-04 added a user walkthru, rate this app button, privacy policy and terms of service url link ### 1.1 — 2026-05-01 the "Inst" button should display the correct set of instructions ### 1.0 — 2026-05-01 No release notes. ## More apps by Sim Ayers - [Rafter Tools+](https://appshunter.io/ios/app/rafter-tools-plus/id689788839) - [Crown Molding Tools](https://appshunter.io/ios/app/crown-molding-tools/id894395519) - [Stair Tangent](https://appshunter.io/ios/app/stair-tangent/id1173630967) - [help-desk](https://appshunter.io/ios/app/help-desk/id6759624979) - [Stair Tangent Dark](https://appshunter.io/ios/app/stair-tangent-dark/id6761790615) - [RafterTools+ Dark](https://appshunter.io/ios/app/raftertools-plus-dark/id6762562883) All apps by Sim Ayers: https://appshunter.io/developer/689788842 --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-06.*