Enter your details and click "Calculate" to see your CoastFIRE number.
function calculateCoastFIRE() {
var targetAnnualSpending = parseFloat(document.getElementById('targetAnnualSpending').value);
var targetRetirementAge = parseFloat(document.getElementById('targetRetirementAge').value);
var currentAge = parseFloat(document.getElementById('currentAge').value);
var annualReturn = parseFloat(document.getElementById('annualReturn').value);
var withdrawalRate = parseFloat(document.getElementById('withdrawalRate').value);
var resultDiv = document.getElementById('result');
// Input validation
if (isNaN(targetAnnualSpending) || targetAnnualSpending <= 0) {
resultDiv.innerHTML = "Please enter a valid Target Annual Spending.";
return;
}
if (isNaN(targetRetirementAge) || targetRetirementAge 100) {
resultDiv.innerHTML = "Please enter a valid Target Retirement Age (18-100).";
return;
}
if (isNaN(currentAge) || currentAge = targetRetirementAge) {
resultDiv.innerHTML = "Please enter a valid Current Age (must be less than Target Retirement Age).";
return;
}
if (isNaN(annualReturn) || annualReturn 20) {
resultDiv.innerHTML = "Please enter a realistic Expected Annual Investment Return (e.g., 0.1% – 20%).";
return;
}
if (isNaN(withdrawalRate) || withdrawalRate 10) {
resultDiv.innerHTML = "Please enter a realistic Safe Withdrawal Rate (e.g., 1% – 10%).";
return;
}
var annualReturnDecimal = annualReturn / 100;
var withdrawalRateDecimal = withdrawalRate / 100;
var yearsToGrow = targetRetirementAge – currentAge;
// Step 1: Calculate the total portfolio needed at retirement
var targetRetirementPortfolio = targetAnnualSpending / withdrawalRateDecimal;
// Step 2: Calculate the CoastFIRE number (present value needed to reach targetRetirementPortfolio)
var coastFireNumber = targetRetirementPortfolio / Math.pow((1 + annualReturnDecimal), yearsToGrow);
resultDiv.innerHTML =
"To achieve your target annual spending of $" + targetAnnualSpending.toLocaleString('en-US', { minimumFractionDigits: 0, maximumFractionDigits: 0 }) + " in retirement at age " + targetRetirementAge + ", you will need a total portfolio of approximately $" + targetRetirementPortfolio.toLocaleString('en-US', { minimumFractionDigits: 0, maximumFractionDigits: 0 }) + "." +
"Based on your inputs, your CoastFIRE number is: $" + coastFireNumber.toLocaleString('en-US', { minimumFractionDigits: 0, maximumFractionDigits: 0 }) + "." +
"This means if you save $" + coastFireNumber.toLocaleString('en-US', { minimumFractionDigits: 0, maximumFractionDigits: 0 }) + " by age " + currentAge + ", and var it grow at an average annual return of " + annualReturn + "% (post-inflation) until age " + targetRetirementAge + ", you will likely reach your target retirement portfolio without needing to save another dollar.";
}
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Understanding CoastFIRE: Your Path to Early Financial Independence
CoastFIRE is a powerful financial independence strategy that allows you to save a significant amount of money early in your career, then let that money grow untouched through compound interest until traditional retirement age. The "Coast" part means you no longer need to contribute new savings to your retirement accounts; your existing nest egg is projected to grow sufficiently on its own to fund your desired retirement lifestyle.
How CoastFIRE Works
The core idea behind CoastFIRE is leveraging the magic of compound interest over a long period. Instead of saving aggressively until your desired retirement age, you front-load your savings. Once you hit your "CoastFIRE number," you can then choose to work less, pursue passion projects, or simply enjoy a less stressful career, knowing your future retirement is already funded.
This strategy is particularly appealing for those who want to achieve financial freedom without necessarily retiring in their 30s or 40s (like traditional FIRE). It offers a middle ground, providing flexibility and reducing financial pressure much earlier in life.
Key Components of the CoastFIRE Calculation
Our CoastFIRE calculator uses several key inputs to determine your personal CoastFIRE number:
Target Annual Spending in Retirement: This is the estimated amount of money you'll need each year to cover your expenses and enjoy your desired lifestyle once you stop working. Be realistic and consider inflation.
Target Retirement Age: The age at which you plan to fully retire and begin drawing from your investments.
Current Age: Your current age, which helps determine the number of years your investments have to grow.
Expected Annual Investment Return (Post-Inflation): This is the average annual growth rate you expect your investments to achieve, adjusted for inflation. A common conservative estimate is 5-7% for a diversified portfolio. Using a post-inflation return simplifies the calculation by giving you a number in today's dollars.
Safe Withdrawal Rate: This is the percentage of your total retirement portfolio you plan to withdraw each year without running out of money. The "4% rule" is a widely cited guideline, suggesting you can safely withdraw 4% of your initial portfolio value (adjusted for inflation) annually.
Example Scenario:
Let's say you are 30 years old and want to retire at 65. You estimate needing $60,000 per year in retirement. You expect an average annual investment return of 5% (post-inflation) and plan to use a 4% safe withdrawal rate.
Target Retirement Portfolio: To withdraw $60,000 annually at a 4% rate, you'll need a portfolio of $60,000 / 0.04 = $1,500,000.
Years to Growth: From age 30 to 65, your money has 35 years to grow.
CoastFIRE Number: Using the compound interest formula in reverse, you would need to have approximately $264,000 saved by age 30. This amount, left untouched and growing at 5% annually, would become $1,500,000 by age 65.
Once you hit that $264,000 mark, you could theoretically stop contributing to your retirement accounts and focus on other financial goals or lifestyle choices, knowing your retirement is on track.
Important Considerations:
Inflation: The calculator uses a post-inflation return, meaning the "Target Annual Spending" you input is in today's dollars. If you use a nominal return, you'd need to inflate your target spending.
Market Volatility: Investment returns are not guaranteed and can fluctuate. The calculator uses an average, so actual results may vary.
Healthcare Costs: Don't forget to factor in healthcare expenses, especially if you plan to retire before Medicare eligibility.
Taxes: The calculator does not account for taxes on withdrawals or capital gains. Plan for these in your overall strategy.
Flexibility: CoastFIRE offers flexibility, but it's wise to periodically review your plan and adjust if your goals or circumstances change.
Use this calculator as a guide to understand the power of early savings and compound interest. It can help you visualize a path to financial freedom that doesn't necessarily require extreme frugality for decades.