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
Lumber Tally Calculator
Lumber Tally Calculator is the fast way to build a truck and tally lumber
$4.99 · In-app purchases
PRICE
$4.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 5.0
2 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
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A product spec, screen plans, and build steps for your coding agent.
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What's included14 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 Lumber Tally Calculator: map the core Business 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
Ensure clear error messages and validations for input fields.
Assumption to check: Users may find the input validation confusing or inconsistent.
Validate with people who use this workflow before building.
Hypothesis 2
Add features like saving and sharing calculations, or integrating with cloud storage.
Assumption to check: Limited functionality compared to more comprehensive calculators.
Validate with people who use this workflow before building.
Hypothesis 3
Introduce themes and personalized settings for a better user experience.
Assumption to check: Lack of user customization options.
Validate with people who use this workflow before building.
Hypothesis 4
Implement offline capabilities to allow use without internet access.
Assumption to check: No offline functionality.
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
Lumber Tally Calculator is the fast way to build a truck and tally lumber. Enter your dimensions, lengths, and unit counts and instantly see board feet, linear feet, and board-foot-weighted average cost — built for lumber traders, brokers, sawmills, and yards. BUILD A TRUCK • Tally any mix of dimensions (2x4 through 4x8, plus custom sizes) and lengths (8'–20') • Live running board-foot and linear-foot totals as you type • Add or remove dimensions on the fly PRICING & COST • Enter price per MBF for any length • Each dimension shows its board-foot-weighted average cost automatically SAVE & REUSE • Save tallies by name — PO, customer, or load • Drag to reorder, reopen, or delete anytime • Every saved truck shows its full per-dimension breakdown, PPU, and average price FAST & PRIVATE • Works completely offline — no account, no sign-in • Everything stays on your device; nothing is collected or uploaded • Clean, distraction-free layout built for quick entry at the desk or in the yard Whether you're pricing a load, building a truck, or quoting a customer, Lumber Tally Calculator does the math so you don't have to.
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
TypeScript
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.
