The Coast FIRE Compound Simulator
A Coast FIRE calculator determines the exact age you can stop contributing to retirement accounts and let compound interest finish the job. Enter your current savings, target retirement number, expected return rate, and current age to see when your investments will coast to your goal on their own.
Enter your numbers below and discover your Coast FIRE age the magical moment your money works harder than you ever did.
Enter your details and hit calculate to discover your Coast FIRE status.
Your compound growth curve will appear here after calculation.
Coast FIRE is the point where your invested portfolio is large enough that even if you never invest another dollar compound interest alone will grow it to your retirement target by your desired retirement age. You've "coasted" to financial independence.
We use the compound interest formula: A = P(1 + r/n)nt, where P is your current portfolio, r is the annual return rate, n is compounding frequency (annually), and t is time in years. We solve backwards to find the minimum P needed today.
Your "Coast Number" is the minimum portfolio value you need right now so that compound growth alone reaches your target. If your current portfolio exceeds this number, congratulations you've already hit Coast FIRE!
This calculator assumes a constant annual return and does not account for inflation, taxes, fees, or market volatility. Real-world returns will vary. Use this as directional guidance, not a precise financial plan. Consult a financial advisor for personalized advice.
Ready to master Coast FIRE? Read The Simple Path to Wealth and grab a personal finance journal to track your journey.
Coast FIRE (Financial Independence, Retire Early) is a milestone where you have enough invested at a young age that compound interest will carry you to your target retirement number without contributing another dime. This Coast FIRE calculator helps you find exactly when that milestone occurs based on your current portfolio, expected return, and retirement goals. CoastCalc operates 100% locally in your browser for absolute privacy.
Coast FIRE is the point where your existing investments, left untouched, will grow to your full retirement number by your target retirement age through compound interest alone. Once you reach Coast FIRE, you only need to earn enough to cover current living expenses — no more retirement contributions required.
Your Coast FIRE number depends on three variables: your target retirement number (typically 25× annual expenses), your current age, and the expected real rate of return (inflation-adjusted, typically 5-7%). The formula is: Coast Number = Retirement Number / (1 + return rate)^(years until retirement).
The S&P 500 has returned approximately 10% nominally and 7% after inflation over long periods (30+ years). However, this includes significant drawdown periods. Conservative planners use 5-6% real returns to account for sequence-of-returns risk and potential lower future returns.