Your Coast FIRE Number
$0
Needed invested today
Full FIRE Number
$0
Target at retirement
Projected at Retirement
$0
If you stop contributing now
Growth With No Further Contributions
My Coast FIRE Plan — Financial Depth
financialdepth.com/coast-fire
Quick Summary (TL;DR)
- Coast FIRE = the amount that, left untouched, grows to your full FIRE number by retirement with no further contributions.
- Formula:
Coast Number = FIRE Number ÷ (1 + real return)years to retirement - Example: a 30-year-old retiring at 65 needing $1.25M, at a 7% real return → only about $117,000 invested today.
- The earlier you start, the smaller the number — time does the heavy lifting. Use a real (after-inflation) return.
What Coast FIRE Means
Coast FIRE is one of the most freeing milestones on the path to financial independence. It's the point where you've invested enough that compound growth alone will carry your portfolio to your full FIRE number by retirement — without adding another dollar. You still need income to cover today's bills, but you're off the hook for retirement saving. That can mean dropping to part-time work, switching to a lower-stress job, or taking a sabbatical while your investments keep working.
The math is your FIRE number discounted back to the present. First, your FIRE number is annual expenses ÷ withdrawal rate. Then the coast number is FIRE Number ÷ (1 + r)years, where r is your expected real return and years is the time until retirement. The further you are from retirement, the smaller your coast number — because compounding has more time to do the work.
Worked example: A 30-year-old who wants to retire at 60 with $40,000/year in spending needs a $1,000,000 FIRE number at a 4% rate. At a 7% real return over 30 years, the coast number is only about $131,000. Invest that much by 30 and, even if you never save again, you're projected to reach $1M by 60. Wait until 40 to hit coast, and the number jumps to roughly $258,000 — time is the single biggest lever.
Frequently Asked Questions
What is Coast FIRE?+
It's the point where you have enough invested that compound growth alone reaches your full FIRE number by retirement, even with zero new contributions. You still cover current costs, but no longer need to save for retirement.
How is the Coast FIRE number calculated?+
It's your FIRE number discounted to today: Coast Number = FIRE Number ÷ (1 + r)^years, where r is your expected return and years is the time until retirement.
What happens after I reach Coast FIRE?+
You can stop saving for retirement and only earn enough to cover current expenses. Many people use it to work part time, switch to more enjoyable work, or take career breaks while investments compound.
Key Considerations
- The real return is your most important assumption. Coast FIRE lives or dies on the growth rate you plug in. Use a real (after-inflation) figure — historically ~7% for stocks, but assuming 5–6% builds in a margin of safety.
- Markets aren't smooth. The formula assumes a steady annual return, but real returns are volatile. A weak first decade can leave you short of the target even if the long-run average holds, so revisit the number periodically.
- The money must stay invested. Coast FIRE only works if you don't touch the principal before retirement. Any withdrawal resets the compounding and pushes your coast number back up.
- Watch your fixed costs. Federal Reserve data discussed in the FIRE community suggests a low housing-to-income ratio is one of the strongest predictors of reaching Coast FIRE — lower fixed expenses mean you need less income to "coast" on.