InvestingFIRE 🔥 — The #1 Interactive FIRE Calculator

InvestingFIRE is a responsive web application for calculating your path to Financial Independence and Early Retirement (FIRE). It features a year-by-year projection engine that simulates both accumulation (savings and investment growth) and retirement (withdrawals) phases.

Deployed version: https://investingfire.com

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🎯 Goal & Vision

Goal

To build the most comprehensive, user-friendly, and transparent open-source financial independence calculator on the web.

Vision

Democratize financial planning by providing professional-grade simulation tools in an accessible, privacy-focused, and beautiful interface. We believe everyone should have the ability to model their financial future without needing a finance degree or expensive software.

Business Model

InvestingFIRE operates on a transparent open-source model:

1. Free Forever Core: The essential calculation tools will always be free and open-source.
2. Community Supported: We rely on community contributions (code & feedback) to improve the tool.
3. Educational Affiliates: We may curate high-quality resources (books, courses, tools) to help users on their journey, keeping the tool free of intrusive ads.

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🗺️ Roadmap

We are actively expanding the capabilities of InvestingFIRE. Below is our plan broken down into phases.

Phase 1: Enhanced Simulation (The Engine)

Focus on making the math more robust and flexible.

• Coast FIRE Mode: Option to stop contributions at a certain age but retire later.
• Barista FIRE Mode: Include part-time income during "retirement" years.
• Monte Carlo Simulations: Add probabilistic outcomes (e.g., "95% chance of success") instead of just deterministic linear growth.
• Variable Withdrawal Strategies: Implement dynamic withdrawal rules (e.g., Guyton-Klinger) beyond just fixed inflation-adjusted withdrawals.

Phase 2: User Experience & Persistence

Make the tool easier to use and return to.

• URL State Sharing: Encode form values into the URL so scenarios can be bookmarked and shared.
• Local Persistence: Automatically save user inputs to localStorage so they don't vanish on refresh.
• Currency & Locale Support: Allow users to select currency symbols and number formatting (USD, EUR, GBP, etc.).

Phase 3: Advanced Features & Analytics

For the power users who need more detail.

• Tax Considerations: Simple toggles for Pre-tax vs. Post-tax estimations.
• Scenario Comparison: Compare two different plans side-by-side (e.g., "Retire at 45 vs 55").
• Data Export: Download projection data as CSV or PDF reports.

Phase 4: Content & Community

• Blog/Guides: Integrate a CMS (like Markdown/MDX) for in-depth financial guides.
• Community Presets: "One-click" setups for common strategies (e.g., "Lean FIRE", "Fat FIRE").

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🚀 Features at a Glance

• ⚡️ Real-Time Projections: Every field updates the chart as you type. Experiment with savings, growth rates, inflation, or retirement age and see your future instantly.
• 📈 Interactive Chart: Dual-area plots for portfolio value and future monthly spending, plus reference lines for FIRE milestones and “4% rule” legends.
• 🧠 Education Baked In: Contextual tooltips, deep-dive sections on how FIRE works, FAQs, and must-read resources included.
• 🔎 Detailed Methodology: Not just a 25x rule — runs a full, year-by-year simulation with inflation-adjusted withdrawals and optional 4%-rule overlays.
• 👌 Modern UX: Typing, sliding, or clicking feels good. Responsive on all devices.

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🧰 How It Works

The calculator models your FIRE journey in two phases:

1. Accumulation:

   • Your starting capital is grown by your expected CAGR (~7% by default).
   • Monthly savings are added for each year until retirement.
   • Every variable can be adjusted live (capital, savings, age, growth, inflation, spending, target retirement).

2. Retirement:

   • Your balance continues to grow by CAGR.
   • Each year, an inflation-adjusted monthly allowance is withdrawn.
   • The simulation runs until your selected life expectancy, showing the possibility of portfolio depletion.

Key Outputs:

• 🔥 “FIRE Number”: Portfolio value at your defined retirement age
• 📊 Interactive projection chart: See how your nest egg and withdrawals evolve over time
• 4️⃣ “4% Rule” overlays: Compare dynamic results to classic rule-of-thumb

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🌟 Try It For Yourself

To run locally:

1. Clone the repo

   git clone https://git.schulze.network/schulze/fire.git
   cd fire
   

2. Install dependencies

   pnpm install
   

3. Run the app

   pnpm run dev
   

4. Visit http://localhost:3000 and unleash the fire.

Running Tests 🧪

We use Vitest for unit testing and Playwright for end-to-end (E2E) testing.

Unit Tests:

pnpm test

E2E Tests:

# First install browsers (only needed once)
pnpm exec playwright install

# Run tests
pnpm test:e2e

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✏️ Inputs & Variables

• Starting Capital — How much you’ve already invested
• Monthly Savings — What you’ll add each month
• Current Age & Retirement Age — Your FI timeline
• Life Expectancy — How long do you want income to last?
• Expected Growth Rate (CAGR) — Portfolio annual % return, before inflation
• Inflation Rate — Cost of living increases
• Desired Monthly Allowance — Your lifestyle, today’s dollars

As you adjust these, all projections update instantly without needing to hit “Calculate.”

Try many “what ifs” fast.

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👩‍💻 Contributing

Pull requests are welcome! Open issues for bugs, new features, or debate about safe withdrawal rates and tax assumptions.

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📄 License

GPL-3.0

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🥇 Why Use InvestingFIRE?

• You want the truth — not just a 4% fantasy.
• You want to learn, not just punch in numbers.
• You want clarity, speed, and modern UI.
• You want to show your friends the best FIRE tool on the web.

Enjoy the rocket ride to financial independence.
InvestingFIRE — Know your number. Change your future.