Fire Calculator

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FIRE Calculator

Calculate your timeline to Financial Independence and Early Retirement

Total yearly spending in retirement.
Current invested assets.
New investments added each month.
Anticipated stock market growth.
Traditional rule is 4%.
Your age today.

Your FIRE Results

Your FIRE Number
Total target portfolio
Years to FIRE
Until you reach your goal
Retirement Age
Age you can stop working
Retirement Year
The calendar year you retire

Understanding the FIRE Calculation

FIRE stands for Financial Independence, Retire Early. This lifestyle movement is defined by frugal living and heavy investing to reach a state where your portfolio yields enough income to cover your living expenses for the rest of your life.

How the FIRE Number is Calculated

The primary calculation behind FIRE is based on the 4% Rule, derived from the Trinity Study. This study suggests that if you withdraw 4% of your portfolio annually (adjusted for inflation), your money has a high probability of lasting 30 years or more.

The formula for your FIRE Number is:

FIRE Number = Annual Expenses / Safe Withdrawal Rate

For example, if you spend $40,000 per year and use a 4% withdrawal rate, your target is $1,000,000 ($40,000 / 0.04).

The Path to Financial Independence

To reach this goal, we calculate the growth of your current assets plus your monthly contributions using compound interest. The math accounts for:

  • Current Savings: Your starting point (Initial Principal).
  • Monthly Contributions: Your regular "fuel" for the FIRE engine.
  • Investment Return: The average annual growth of your stocks, bonds, or real estate.

Realistic FIRE Example

Let's look at a 30-year-old with $50,000 saved, investing $2,000/month. If they spend $40,000 annually and expect a 7% market return:

  • FIRE Number: $1,000,000 (at 4% SWR).
  • Time to Goal: Approximately 18.5 years.
  • Retirement Age: 48.5 years old.

By increasing the monthly contribution or decreasing annual expenses, the retirement age drops significantly due to the power of compounding.

function calculateFIRE() { var expenses = parseFloat(document.getElementById('annualExpenses').value); var currentSavings = parseFloat(document.getElementById('currentSavings').value); var monthlyContribution = parseFloat(document.getElementById('monthlyContribution').value); var annualReturn = parseFloat(document.getElementById('annualReturn').value) / 100; var withdrawalRate = parseFloat(document.getElementById('withdrawalRate').value) / 100; var currentAge = parseFloat(document.getElementById('currentAge').value); if (isNaN(expenses) || isNaN(currentSavings) || isNaN(monthlyContribution) || isNaN(annualReturn) || isNaN(withdrawalRate) || isNaN(currentAge)) { alert("Please enter valid numbers in all fields."); return; } // 1. Calculate FIRE Number var fireNumber = expenses / withdrawalRate; // 2. Calculate Years to reach FIRE Number // Future Value = PV(1+r)^n + PMT[((1+r)^n – 1) / r] // We solve for n (months) var monthlyRate = annualReturn / 12; var months = 0; var currentBalance = currentSavings; if (currentBalance >= fireNumber) { months = 0; } else if (monthlyContribution <= 0 && annualReturn <= 0) { months = Infinity; } else { // Iterate to find months (more precise for complex monthly compounding) var maxMonths = 1200; // 100 years cap while (currentBalance < fireNumber && months = 100) { document.getElementById('yearsToFireDisplay').innerText = '100+ Years'; document.getElementById('retirementAgeDisplay').innerText = 'N/A'; document.getElementById('retirementYearDisplay').innerText = 'N/A'; } else { document.getElementById('yearsToFireDisplay').innerText = years.toFixed(1) + ' Years'; document.getElementById('retirementAgeDisplay').innerText = retirementAge.toFixed(1); document.getElementById('retirementYearDisplay').innerText = retirementYear; } document.getElementById('fireResults').style.display = 'block'; // Scroll to results document.getElementById('fireResults').scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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