Coast FIRE Calculator
Find the portfolio balance you need today so compound growth alone reaches your FIRE number by retirement — no more contributions required. Includes a by-age chart showing the threshold at every age.
Your Numbers
Real return: 3.9%
Coast FIRE threshold vs. your portfolio by age
Where the orange line (your portfolio coasting) crosses the gray line (threshold needed) is when you hit Coast FIRE.
How this calculator works
Coast FIRE is reached when your current portfolio is large enough that compound growth alone — with zero future contributions — reaches your full FIRE number by retirement age.
The formula uses present-value math:
Where r is the real (inflation-adjusted) annual return and years is the time until retirement. Using the test values (expenses $50K, 4% WR, 5% return, age 30, retire 60, savings $120K): FIRE = $1,250,000 | Coast = $1,250,000 ÷ 1.05³Ⱐ≈ $289,222. Since $120K < $289,222, Coast FIRE has not yet been reached.
The chart's dashed gray line shows the threshold required at each age — it declines as you approach retirement because less time is needed for compounding. The orange line shows your portfolio growing from today's savings at the selected return rate (with no contributions). They cross at the age you'd first hit Coast FIRE.
Frequently Asked Questions
What is my Coast FIRE number?
Your Coast FIRE number is the portfolio balance you need today so that — even if you never contribute another dollar — compound growth alone will reach your full FIRE number by your target retirement age. Once you hit your Coast FIRE number, you only need to earn enough to cover current living expenses, not save aggressively for retirement.
How is the Coast FIRE number calculated?
The coast fire calculator uses present-value math: Coast FIRE = FIRE Number ÷ (1 + real return)^years to retirement. For example, with a $1,250,000 FIRE number, a 5% real return, and 30 years to retirement: $1,250,000 ÷ (1.05)^30 ≈ $289,222. If your current portfolio exceeds that figure, you've hit Coast FIRE.
How does my Coast FIRE number change by age?
Your Coast FIRE number decreases as you get older because there are fewer years left for compounding. The chart plots the exact threshold at every age between now and your target retirement — where the orange line (your coasting portfolio) crosses the gray threshold line is the age you first achieve Coast FIRE.
How is Coast FIRE different from Barista FIRE and full FIRE?
Full FIRE means your portfolio generates all income and you never work again. Coast FIRE means your portfolio will grow to cover retirement on its own, but you still work to cover today's bills. Barista FIRE means working part-time while a smaller portfolio covers the gap between that income and your expenses. Coast and Barista FIRE are often used as intermediate milestones on the path to full financial independence.
What return rate should I assume in the coast fire calculator?
The US stock market has historically averaged roughly 10% nominal, or about 7% after inflation. For a diversified portfolio including bonds, 5–7% nominal is a reasonable planning range. This calculator separates the nominal return and inflation into two sliders so you can see the real return explicitly — the default is 7% nominal and 3% inflation, giving a 3.9% real return.