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
Home Builder Pro Calcs
"Love this app makes my job much easier." - Danny O'Dea
$9.99 · In-app purchases
PRICE
$9.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.7
1,072 ratings · Top 15%
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.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included17 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 Home Builder Pro Calcs: 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
Expand the variety of calculators offered.
Assumption to check: Limited calculator options compared to competitors
Validate with people who use this workflow before building.
Hypothesis 2
Enhance stability and testing across devices.
Assumption to check: Occasional crashes on specific devices
Validate with people who use this workflow before building.
Hypothesis 3
Allow users to create custom calculators.
Assumption to check: No custom calculator feature
Validate with people who use this workflow before building.
Hypothesis 4
Improve clarity on what is included in each subscription tier.
Assumption to check: In-app purchase confusion for features
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
"Love this app makes my job much easier." - Danny O'Dea Thank you for your calculator suggestions. Now with 440 home improvement calculations and unit conversions Home Builder Pro Calcs gives you access to quickly and easily solve a variety of calculations including hours and cost estimates and take off quantities. Calculations can be saved and emailed. Easy to use and understand inputs and results in either decimals or fractions. Rich support for U.S., imperial, and metric measurements. Built-in calculator with support for ft/in and fractions. Current Calculators include: Business * 28 calculators for loans, pricing, travel costs, and more. Concrete & Paving * 11 calculators for asphalt, concrete, paver bricks, and more. Electrical * 5 different calculators Floors, Walls & Ceilings * 13 calculators for carpet, drywall, wall covering, tile, paint, and more. Foundations * 33 calculators for foundations, soil, grading, rebar, etc. Framing * 19 calculators for balusters, joists, studs, siding, stairs, and more Heating & A/C * 8 calculators for airflow, attics, fans, air conditions, insulation... Hours Estimates * Effort Factor * Over 55 different estimators for: * Carpentry - finish, siding, stairs, walls, ... * Concrete - blocks, bricks, concrete, reinforcement, tile, ... * Doors & Windows - garage doors, glass, metal, windows, wood, ... * Finishes - carpet, paint, wood floors, stucco, plaster, tile, .... * Roofing - roofing, sheathing, sheet metal, ... * Site Work - concrete demolition, excavation, stumps, trees, forms, culverts, landscape, ... Landscape & Yard * 15 calculators for fence, fertilizer, mulch, seeds, trees, mowing and more. Masonry * 8 calculators for walls, joints, core filling,... Miscellaneous * Area, Volume & Angle - 25 calculators for a variety of shapes. * Conversions - 26 different unit conversions * Glossary - Over 370 terms * 11 calculators for tanks, pulleys, weather, wrenches, ... Roof Framing and Roofing * 22 calculators for rafters, ridges, gables, pitch, trusses, shingles and more Wood & Materials * 20 calculators for lumber, nails, plywood, caulking, etc. You may also purchase add-on packs within the app. There are currently two add-ons available: Project Dates & Times * Over 35 calculators help you understand and manage project timing and deadlines. Sensor Angle * A set of 10 calculators that use the angle sensing ability of your iPhone or iPad to easily and accurate measure an angle and calculate a variety of other angles and lengths. Map Estimator * Estimate the distance and area using a map. Great for estimating size of yard, length of fence, etc. If there's a calculator you'd like to see added, visit our website and send us an email.
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
Zustand
React Navigation
react-native-paper
react-native-async-storage
BUILD KIT DIFFICULTY
Intermediate
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.
