Coast FIRE Calculator
$
$
7%
30 yr
Coast FIRE Number$131,367.12
Not Coast-FI yet$31,367.12 to go
Projected Nest Egg at Retirement$761,225.50
Coast FIRE is the point where your invested savings are large enough that compound growth alone will reach your retirement target by the time you stop working, without adding another dollar. This calculator discounts your FIRE target back to today using your expected return and years left, giving the coast number you need right now and telling you whether you have already crossed it.
Formula
coastNumber = fireTarget / (1 + r)^years
- fireTarget
- Portfolio value you want at retirement
- r
- Expected annual return as a decimal (e.g. 0.07)
- years
- Years remaining until retirement
How it works
- Enter your FIRE target (the portfolio you want at retirement), your current invested savings, an expected annual return, and the number of years until you retire.
- The calculator discounts the target back to today: coast number = target divided by (1 + return) raised to the number of years. If your current savings meet or beat that figure, you are Coast-FI.
- It also projects your current savings forward at the same return so you can see the nest egg they would grow into with zero further contributions.
Worked example
A 35-year-old wants a $1,000,000 portfolio at 65 and expects a 7% return.
- Growth factor = 1.07^30 = 7.6123.
- Coast number = 1,000,000 / 7.6123 = $131,367.12.
- With $131,367 invested today and no new savings, the portfolio coasts to $1,000,000 by 65.
Coast FIRE number is about $131,367; reach it and you can stop contributing.
Frequently asked questions
- What is the difference between Coast FIRE and regular FIRE?
- Regular FIRE means you have enough to retire now. Coast FIRE means you have enough invested that growth alone will get you there by your target date, so you only need to cover current living expenses until then.
- Why does the coast number get smaller with more years to retirement?
- A longer runway gives compounding more time to work, so a smaller amount today can grow into the same target. The number is the target divided by a larger growth factor.
- What return rate should I use?
- Many planners use a real (inflation-adjusted) return of 5% to 7% for a diversified stock-heavy portfolio. Use a conservative figure if you want a safety margin, since the coast number is sensitive to this input.