Keep contributing 500/month and you reach Coast FIRE around age 33. From then on, compounding alone carries you to your FIRE number by age 65.
How the math works
Your retirement (FIRE) number follows the 4% rule:
FIRE Number = Monthly Expenses × 12 × 25 Coast FIRE Number today = FIRE Number ÷ (1 + r/12)^T where r = expected annual return, T = months to retirement age
If your portfolio already exceeds the Coast FIRE number, compounding alone reaches your FIRE number by your target age — you are coasting. If not, the calculator simulates your monthly contributions and finds the age at which the coast check first passes.
The Coast FIRE prediction in the Wealth Path app runs this same check across your real assets — each compounding at its own expected return — and updates your coast date automatically as your balances change. See also the Early Retirement Scenario for full retirement planning with withdrawals.
The 25× target above rests entirely on the 4% rule, which is a rule of thumb from 1990s US market research — not a guarantee. Our guide to the 4% rule covers where the number came from, what it assumes, and why early retirees usually plan around a lower rate.
Frequently Asked Questions
What is Coast FIRE?
Coast FIRE is the point where your portfolio is large enough that compounding alone — with no further contributions — will grow it to your retirement number (25× annual expenses, the 4% rule) by your target retirement age. After reaching it, you only need to earn enough to cover your living costs.
How is my Coast FIRE number calculated?
Your FIRE number is monthly expenses × 12 × 25. Your Coast FIRE number today is that FIRE number discounted back by monthly compounding at your expected return: FIRE ÷ (1 + r/12)^months-to-retirement. If your portfolio is above it, you are already coasting.
Should I adjust for inflation?
If you want the FIRE number in future money — what your expenses will actually cost at retirement age — enable the inflation rate. Your target grows to match, which makes the Coast FIRE number today more conservative.
Is the 4% rule reliable?
The 4% rule is a widely used heuristic based on historical withdrawal studies, not a guarantee. It assumes a diversified portfolio and a roughly 30-year retirement. Treat Coast FIRE as a planning milestone and revisit it as markets and your expenses change.
Get your real Coast FIRE date
Wealth Path tracks your actual portfolio and recalculates your Coast FIRE date as your balances grow — plus 10 more predictions from debt payoff to passive income.
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The information and calculations provided are for informational and educational purposes only and should not be considered financial, investment, or professional advice. Projections are hypothetical, based on assumptions that may not reflect actual market conditions. Past performance does not guarantee future results, and all investments carry risk of loss. Consult a qualified financial professional before making financial decisions.