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
Annular Volume Calculator
Annular Volume Calculator is a must-have tool designed for oilfield professionals, but it's also perfect for anyone needing to calculate the annular volume between two pipes or between a hole and a pipe
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
N/A
No ratings yet
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 included15 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 Annular Volume Calculator: map the core Reference 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
Implement a feedback system to gather user reviews.
Assumption to check: Lack of user reviews and ratings can deter new users
Validate with people who use this workflow before building.
Hypothesis 2
Expand functionality to include more shape calculations.
Assumption to check: Limited calculation options may not meet all user needs
Validate with people who use this workflow before building.
Hypothesis 3
Enhance UI with animations and modern design patterns.
Assumption to check: Basic UI may lack engagement
Validate with people who use this workflow before building.
Hypothesis 4
Add share functionality to allow users to share results easily.
Assumption to check: No social sharing 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
Annular Volume Calculator is a must-have tool designed for oilfield professionals, but it's also perfect for anyone needing to calculate the annular volume between two pipes or between a hole and a pipe. Whether you're in the field or the office, this app simplifies your volume calculations, helping you work efficiently and accurately. Key Features: • Easily switch between Oilfield Units (US customary) and Metric Units. • Input the Inside Diameter (ID) of the larger pipe or hole, the Outside Diameter (OD) of the smaller pipe, and the height or depth to instantly calculate the annular volume. • Choose your desired output units, including cubic feet, barrels, gallons (US), or cubic meters and liters (Metric). • Built on the latest American Petroleum Institute (API) standards. • Professionally verified with leading oilfield service companies. • Tested and proven in real-world conditions across the US, Canada, UAE, and Oman. Why Annular Volume Calculator? - Quick Calculations: Fast and reliable results when you need them most. - Enhanced Safety: Minimize errors to ensure safe and efficient operations. For support or feedback, feel free to contact us at [email protected].
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
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zustand
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.
