Ever wondered what that coffee could have been worth if you'd invested instead?
The Fumble Machine is an opportunity cost calculator that shows you the true cost of your past purchases. Enter what you bought, when you bought it, and what you could have invested in instead — and watch as we calculate how much you "fumbled."
Ever bought something and later thought, "What if I had invested that money instead?"
The Fumble Machine answers that question with brutal honesty.
Example:
- You bought a $50 video game in January 2020
- Instead, you could have bought Bitcoin
- That $50 would be worth $500+ today
- You fumbled $450 💀
Enter your purchase in your local currency — USD, EUR, GBP, INR, JPY, and more. We handle all the conversions automatically.
Powered by Yahoo Finance API with accurate historical prices for:
- Cryptocurrencies — Bitcoin, Ethereum, and more
- Stocks — Apple, Tesla, NVIDIA, Amazon, Google
- Indices — S&P 500, and other major indices
- Global Markets — Indian stocks (NSE/BSE), European markets, and more
Get a beautifully designed receipt showing your fumble that you can:
- Download as an image
- Share on Twitter/X
- Post on Reddit
- Copy the link
Looks great on any device with a responsive, modern UI.
Each fumble comes with a personalized message like:
- "That's enough for a new smartphone"
- "That's enough for a down payment on a house"
- "That's enough for retiring 5 years early"
- Visualize the opportunity cost of impulse purchases
- Build awareness about investment potential
- Make better spending decisions
- Teach the power of compound growth
- Demonstrate "time in the market" concepts
- Show real-world examples of opportunity cost
- Create shareable content about "fumbles"
- Engage with communities on Twitter, Reddit, and more
- Compare notes with friends on biggest misses
- Financial influencers showcasing market history
- Meme-worthy content for social media
- Educational material for courses or blogs
- Enter your purchase — What did you buy and how much did it cost?
- Pick the date — When did you make that purchase?
- Choose what you missed — Bitcoin? Tesla? S&P 500?
- See the damage — We calculate exactly how much you fumbled
- No account required
- No directly identifying information is collected
- Optional aggregate analytics store country, selected asset, currency, calculated fumble amount, and emoji reactions — never your purchase description or an account identifier
- All calculations happen in real-time
- Open source and transparent
Built with modern technologies:
- Next.js 15 — React framework with App Router
- TypeScript — Type-safe development
- Tailwind CSS — Utility-first styling
- Yahoo Finance API — Real-time and historical market data
- Vercel — Deployment and analytics
Click to expand development instructions
- Node.js 18+
- npm or yarn
# Clone the repository
git clone https://github.com/MrForward/Fumble-Machine.git
cd Fumble-Machine
# Install dependencies
npm install
# Run development server
npm run devOpen http://localhost:3000 to see the app.
For production with caching enabled, set up Supabase:
- Create a free project at supabase.com
- Run the SQL schema from
supabase/schema.sqlin the SQL Editor - Add environment variables to Vercel:
NEXT_PUBLIC_SUPABASE_URL=https://your-project.supabase.co
SUPABASE_SERVICE_KEY=your-service-role-keyWithout Supabase, the app still works using in-memory caching (resets on deploy).
src/
├── app/
│ ├── api/ # Server-side API routes
│ ├── globals.css # Global styles
│ ├── layout.tsx # Root layout
│ └── page.tsx # Main page
├── components/ # React components
│ ├── confession-form.tsx
│ ├── receipt.tsx
│ └── share-button.tsx
└── lib/ # Utilities and helpers
Deploy instantly with Vercel:
MIT License — feel free to use, modify, and share.
- Market data powered by Yahoo Finance
- Built with Next.js by Vercel
- Inspired by the regret of every investor who said "I should have bought earlier"
Stop fumbling. Start investing.
Try The Fumble Machine →