Build an Amazon FBA Calculator with Claude Code

Build an Amazon FBA Calculator web app. People search for "amazon fba calculator" about 24,000 times a month, plus related searches like "amazon fba profit calculator", "fba fee calculator", "amazon seller calculator". The goal is a tool that ranks for those searches and makes money.

What it should do:
Build an Amazon FBA calculator web app. Create a homepage with product details input (price, cost, weight, dimensions) and marketplace selector. Add comprehensive fee breakdown: referral fees, FBA fees, storage costs, and shipping. Show profit calculations with margin percentages and ROI analysis. Include scenario comparison tools and break-even analysis. Add export functionality and saved calculation history. Use Amazon-inspired orange and blue branding with clear financial displays. Focus on fee calculation and profit analysis first.

How to build it:
1. Read this folder first. If it is empty, set up Next.js (App Router, TypeScript, Tailwind). Write a short PLAN.md with the pages, components, any library or API you need, and what you are leaving for later. Then build.
2. Put the tool itself on the homepage so a visitor can use it within seconds, with no sign-up. Do the processing in the browser where you can, so it is fast and cheap to run. Look at how Amazon Revenue Calculator, Jungle Scout, Helium 10 do it and make ours simpler and faster.
3. Make it rank. Use "amazon fba calculator" in the title tag, H1 and meta description. Under the tool, add a short how-to and an FAQ with FAQPage schema, and add a sitemap and robots.txt. Scaffold these programmatic pages from one template and a data file: /amazon-fba-calculator-[category], /fba-profit-calculator-[marketplace], /calculate-fba-fees-[product-type].
4. Monetisation: Freemium: 10 calculations/day, $12/mo unlimited + advanced analytics. Add a pricing page and the free usage limit, and leave Stripe checkout as a clearly marked stub with the environment variables it needs.
5. Run it locally and test the main flow end to end, including edge cases like empty input and very large files. Fix what breaks, then finish with a summary of what works, what is stubbed and how to deploy it to Vercel.

Paste it into Claude Code in an empty folder. It plans first, so read PLAN.md and steer before it starts building.