Coast FIRE is a financial independence milestone where you have saved enough that compound growth alone can carry your portfolio to a traditional retirement number, without adding another dollar of contributions.
After reaching Coast FIRE, you can switch to a lower-stress job, work part-time, or simply save less aggressively while your existing investments grow in the background. You are not fully retired, but you no longer need to sprint toward every savings goal.
Your Coast FIRE number
Your coast number is the portfolio size today that, left untouched until retirement age, will grow to cover your future spending. It depends on your current age, planned retirement age, expected return, and how much you plan to spend in retirement.
A younger person with more years for compounding needs a smaller coast number than someone closer to retirement. At 7% real returns, money roughly doubles every decade, so a 30-year-old coasting to 65 has 35 years of growth working for them.
If you need $1,000,000 at age 65 and you are 35 today with 7% returns, your coast number is roughly $131,000. That is far less than the full FI number you would need to retire today.
Coast FIRE vs. full FIRE
Full FIRE means your portfolio can fund your lifestyle now, not decades from now. Coast FIRE means you are done with the heavy lifting of saving but still plan to work until traditional retirement age, or at least until your coast portfolio matures.
Coast FIRE appeals to people who want financial security without extreme frugality or leaving their career immediately. You trade the freedom of early retirement for a more relaxed path with lower savings pressure.
Some people reach Coast FIRE in their 30s and then take lower-paying but more fulfilling work, knowing their retirement is already funded by past savings.
Key assumptions and risks
Coast FIRE math assumes you stop contributing but also stop withdrawing before retirement. If you dip into the coast portfolio for emergencies or lifestyle spending, you may need to keep saving.
Return assumptions matter. A 7% average is common in planning, but actual markets vary. A conservative planner might use 5–6% real returns, which raises the coast number.
Inflation-adjusted spending targets should reflect your expected retirement lifestyle, not today's spending. Healthcare costs and lifestyle changes can shift the target significantly.
Calculate your coast number
Enter your age, retirement age, current portfolio, expected return, and retirement spending to see whether you have already hit Coast FIRE and how much more you need.
Use the Coast FIRE calculator for your personal coast number, then compare it against Lean, Barista, and Full FIRE paths with the FIRE comparison tool.