Build a SaaS MRR Calculator with Claude Code

Build a SaaS MRR Calculator web app. People search for "saas mrr calculator" about 100 times a month, plus related searches like "mrr calculator", "saas revenue calculator", "recurring revenue calculator". The goal is a tool that ranks for those searches and makes money.

What it should do:
Create a SaaS MRR calculator with subscription data inputs (new MRR, churned MRR, expansion MRR). Calculate net MRR growth, churn rate, and revenue projections. Include growth charts, cohort analysis, and SaaS metric benchmarks. Add scenario planning and growth forecasting tools. Focus on getting accurate MRR calculations working 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 ChartMogul, Baremetrics, ProfitWell do it and make ours simpler and faster.
3. Make it rank. Use "saas mrr 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: /saas-mrr-calculator-[company-size], /recurring-revenue-[subscription-type], /saas-metrics-[business-stage].
4. Monetisation: Freemium: Basic calculations, $18/mo premium + forecasting. 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.