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
Box Fill Calc NEC
NEC box fill calculator for electricians, apprentices, and electrical engineers.
$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.
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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 included15 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
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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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Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Box Fill Calc NEC: 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
Create a user-friendly input method with clear labels and examples.
Assumption to check: Users often find box fill calculators confusing and unintuitive.
Validate with people who use this workflow before building.
Hypothesis 2
Implement a robust history feature that allows users to easily retrieve past calculations.
Assumption to check: Limited history tracking and results retrieval.
Validate with people who use this workflow before building.
Hypothesis 3
Add comprehensive settings to customize NEC standards and preferences.
Assumption to check: Lack of detailed settings options for customization.
Validate with people who use this workflow before building.
Hypothesis 4
Provide clear explanations of the benefits of in-app purchases and offer a free trial.
Assumption to check: In-app purchases can be confusing.
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
NEC box fill calculator for electricians, apprentices, and electrical engineers. Calculate box fill volumes instantly using official NEC 2023 Article 314.16 data (Tables 314.16(A) and 314.16(B)). No internet required - works 100% offline on the job site. FEATURES: - All standard metal box types: Device, Round/Octagonal, Square 4", Square 4-11/16", Masonry, FS, FD - Custom volume entry for non-standard boxes - Conductor sizes: 18 AWG to 6 AWG per Table 314.16(B) - Internal cable clamps, fixture studs, and hickeys - Multi-gang device fill calculation - Equipment grounding conductors (EGC) with NEC 2023 rules - Isolated grounding conductors - separate allowance - Visual PASS/FAIL indicator with fill percentage - Shows minimum box volume needed when over-filled - Suggests a standard box that will pass PRO FEATURES (one-time purchase): - No ads - Save calculation history - Export calculations as PDF reports - Dark theme support BUILT FOR THE JOB SITE: This app is designed by electricians, for electricians. The interface is clean, fast, and works with one hand. Add conductors, check your fill, and move on - no complicated menus or unnecessary features. ACCURATE NEC DATA: All box volumes are sourced from NEC 2023 Table 314.16(A). Conductor volume allowances follow Table 314.16(B) exactly. Fill rules follow Article 314.16 for conductors, clamps, support fittings, devices, and grounding conductors. Always verify calculations against the official NEC code book before installation. NEC 314.16 FILL RULES: - Each conductor: volume from Table 314.16(B) based on AWG size - Internal clamps: 1× largest conductor volume (all clamps combined) - Support fittings: 1× largest conductor per fitting type - Devices: 2× largest conductor per gang - EGC (≤4): 1× largest EGC volume - EGC (>4, NEC 2023): additional allowance per conductor - Isolated grounds: counted separately PERFECT FOR: - Licensed electricians - Electrical apprentices - Electrical engineers and designers - Electrical contractors - DIY electrical projects - NEC code exam preparation (Journeyman & Master) OFFLINE & PRIVACY: - Works 100% offline - no internet needed - No account required - No data collection - Your calculations stay on your device Simplify your box fill calculations on the job site.
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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
Axios
Expo Clipboard
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.
