App Overview

RPN 28x Calc icon

RPN 28x Calc

tredje design · Productivity

RPN 28x Calc is a programmable scientific calculator with a pleasingly classic look

$6.99 · In-app purchases

PRICE
$6.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
5.0
33 ratings · Top 5%

Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.

Build your own version

Build Kit

Make this idea yours

A product spec, screen plans, and build steps for your coding agent.

First kit free with a verified email

Add to a Remix

Combine features and design from your favorite apps.

Kit ready. Verify your email to download it.

What's included18 files

A product spec, phased build plan, differentiation notes, and screen references.

  • START_HERE
  • AGENTS
  • EVIDENCE
  • SPEC
  • BUILD_PLAN
  • DIFFERENTIATION
  • skills/
  • screens/
Preview a sample Build Kit No email needed

Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.

Feature spec

Goal: Send a clear invoice after finishing a job.

  • Add a client, line items, a due date, and payment instructions.
  • Preview the total before exporting a PDF.
  • Keep an editable draft if export fails.

Screen plan

Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.

States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.

Differentiate and validate

Hypothesis: Contractors need faster repeat invoices more than more templates.

First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.

The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.

Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.

JavaScript is required to complete mailbox verification.

Free quick prompt For a smaller starting point

Quick prompt

> SELECT BUILD PLATFORM:

Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.

// RORK SYSTEM PROMPT
Rork plan preview for RPN 28x Calc: map the core Productivity workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
            

Preview ready. Verify your email to reveal and copy the full prompt.

JavaScript is required to complete mailbox verification. Return to this prompt preview.

Continue in Rork copies the full prompt to your clipboard first, then opens Rork in a new tab.

Continue in Rork >

Affiliate link: CloneChart may earn a commission at no extra cost

Opportunities

AI-GENERATED OPPORTUNITY HYPOTHESES

These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.

Hypothesis 1

Allow users to customize button layouts and themes.

Assumption to check: Limited customization options for users

Validate with people who use this workflow before building.

Hypothesis 2

Add advanced mathematical functions for scientific calculations.

Assumption to check: No support for complex scientific functions

Validate with people who use this workflow before building.

Hypothesis 3

Implement filtering or categorization for calculation history.

Assumption to check: History can become cluttered

Validate with people who use this workflow before building.

Hypothesis 4

Create an onboarding tutorial to guide new users through features.

Assumption to check: No tutorial for new users

Validate with people who use this workflow before building.

App evidence

Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.

App Store description

RPN 28x Calc is a programmable scientific calculator with a pleasingly classic look. Despite its nostalgic appearance, it offers a modern and intuitive user experience, allowing you to interact with your operands by touching them in the display. It is a reverse-polish notation (RPN) calculator with a dynamic stack display. As you add more values to the stack, the display shown on an iPad automatically expands. To see more lines, simply swipe to scroll. You can also re-order the levels or modify any of the values on the stack. ----- "It’s the third RPN calculator I buy for my iPad 2 and the first that makes me happy. It’s graphically appealing, intuitive and very responsive. I rated it 5 stars." (Nuno Gomes) ----- Advanced commands are available in a secondary panel on iPad or as alternative button pages on iPhone. The buttons are efficiently grouped into five pages that you can quickly access by swiping left or right: - user-defined buttons, - letters A-Z for typing, - trigonometric, logarithmic, and data manipulation commands, - statistics, storage and programming commands - binary integers, system flags and boolean logic. This is why RPN 28x Calc is unique in its class: - You can tap a row to select it and issue commands for the selected level. - In REORD mode, it is possible to rearrange the stack by dragging the rows. - You can swipe up or down the display to see all levels. - When you enter a value, you can tap a digit to reposition the cursor. - Tap on the status indicators in the top of the display to change their state. - Drag buttons to re-arrange them as you like it (enable that in the settings). Additionally, on iPad: - The display automatically resizes to show more than just 4 levels of the stack. - You can slide the secondary panel out of view or swipe across the panel to navigate between button pages. New: - 147 scientific units and elementary physical constants. - Upper-tail probablity distribution commands. - Interactive program debugging. RPN 28x Calc is all you need. - High precision arithmetics. - Supports multiple data types: real numbers, complex numbers, binary integers, or lists, arrays, vectors, matrices, programs, names, and strings. - Name your own variables; inspect them in the variable viewer. - Use the rich command set to write your own programs. - Create buttons for your programs. - Interactive button reordering. - Browse all scientific units and constants in the units viewer. - View the command history and the results in the log viewer. - Customizable button click & alert volumes. - Support for landscape orientation. - Optional thousand separators. - Haptic feedback on iPhone. - External keyboard support. - Dark Appearance since iPadOS 13 or iOS 13. - Alternative, dark app icon. - Use the same app on iPad or iPhone. - Use the calculator in iPad multitasking, i.e. in a Slide Over view or in Split View. - No ads, no tracking, and no rating requests. - Downloadable user guide with introduction and command reference (PDF). ----- Plans for future versions (NOT YET SUPPORTED): - Arithmetic expressions.

Written user reviews are not shown here. Check current App Store reviews >

Screenshots

< Scroll to see more >

Build scope

Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.

Define the first version

Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.

Set boundaries

Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.

Check the hard parts

Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.

SUGGESTED BUILD STACK
React Native
Expo
Redux Toolkit
React Navigation
React Native Async Storage
Expo Audio
BUILD KIT DIFFICULTY
Advanced

From the Build Kit assessment.

A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.