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.
App Overview
Workman's Calculator Pro
The calculator has been rebuilt, and it's built for the trades!
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.0
50 ratings · Top 30%
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
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A product spec, screen plans, and build steps for your coding agent.
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What's included16 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.
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.
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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Workman's Calculator Pro: map the core Utilities workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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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
Add more complex calculations and features like graphing.
Assumption to check: Limited advanced features compared to more comprehensive calculator apps.
Validate with people who use this workflow before building.
Hypothesis 2
Implement a cleaner, more organized UI.
Assumption to check: Interface may feel cluttered with too many options.
Validate with people who use this workflow before building.
Hypothesis 3
Include a dark mode option to enhance user experience.
Assumption to check: No support for dark mode which may deter some users.
Validate with people who use this workflow before building.
Hypothesis 4
Add features to share results via clipboard or social media.
Assumption to check: No export or share functionality for results.
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
The calculator has been rebuilt, and it's built for the trades! Workman's Construction Calculator is the best, and simplest construction calculator available on the App Market. With the most intuitive way to calculate measurements. Work with Feet, inches, yards, meters, and regular numbers. Simultaneously! Never before has a calculator worked like this! Do you want to put in 3/16 of an inch? Press the numerator button, click 3, and click 16 afterward, done. Yes, 16. One of the unique parts of Workman's Calculator is that the buttons change. When selecting a numerator only odd values are shown (1, 3, 5, 7, 9). After clicking one of the values the appropriate denominator values appear. If the numerator is 9 or higher, automatically 16 is selected. The denominators will always be more than the numerator. Need to multiply by a decimal? Go ahead. Choose how you wish to view your calculations. • Feet • Inches • Decimals Workman's Calculator is about being quick and getting you your calculations that you need, so there's more time getting done what needs to be done and less time on the phone.
Written user reviews are not shown here. Check current App Store reviews >
Screenshots
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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
@react-native-clipboard/clipboard
@react-native-async-storage/async-storage
react-native-reanimated
expo-router
BUILD KIT DIFFICULTY
Starter
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.
