Coast FIRE Calculator
Enter your age, retirement spending and savings to see your Coast FIRE number and when you reach it.
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4% is the classic rule of thumb
- FIRE number at retirement
- $1,000,000
- Years to retirement
- 30
- Your savings grown to retirement
- $432,194
- Age you reach Coast FIRE
- not before retirement
How this was calculated
- FIRE number = yearly spending ÷ withdrawal rate = $40,000.00 ÷ 4% = $1,000,000.
- Coast number = FIRE number ÷ (1 + 5%)^30 = $231,377.
- Your $100,000 grows to $432,194 by age 65 with no more contributions.
Educational projection with a constant real return; markets vary and the 4% rule is a rule of thumb, not a guarantee. Not financial advice.
What Coast FIRE means
Coast FIRE is the point where you have already invested enough that, even if you never contribute another dollar, compound growth will carry your portfolio to a full retirement nest egg by your target age. From then on you only need to earn enough to cover today's living costs, which is why people use it to switch to lower-stress or part-time work. This Coast FIRE calculator shows the amount you need invested today and how far you are from it.
The formula
- FIRE number = yearly retirement spending ÷ safe withdrawal rate.
- Coast FIRE number = FIRE number ÷ (1 + real return) ^ years until retirement.
Use a real return, meaning after inflation, and spending in today's dollars so inflation does not need a separate step. A 5% real return is a common planning assumption, but it is an assumption: stock returns are not smooth.
Worked example
You plan to spend $40,000 a year in retirement. At a 4% withdrawal rate your FIRE number is $40,000 ÷ 0.04 = $1,000,000. You are 35 and want to retire at 65, so there are 30 years of growth. At a 5% real return, 1.05^30 ≈ 4.32, so your Coast FIRE number is $1,000,000 ÷ 4.32 ≈ $231,377. If you already have $231,377 invested, you have reached Coast FIRE; with $100,000 you are about $131,000 short, and adding a yearly contribution shows the age at which you cross the line.
Why the 4% rule is only a starting point
The 4% rule comes from Bengen (1994) and the Trinity study, which tested 30-year retirements in US history. Someone retiring early may need a lower rate because the portfolio must last longer. Social Security can reduce the number you need: the SSA's my Social Security tool estimates your benefit, and you can subtract it from your spending. Healthcare before Medicare at 65 is a large cost that many Coast FIRE plans underestimate.
Common mistakes
- Using a nominal return with today's dollars, which overstates how fast money grows.
- Forgetting that you still need to cover current expenses, so Coast FIRE is not "stop saving and stop working".
- Counting home equity or cash you will not invest in the savings figure.
Frequently asked questions
What is Coast FIRE?
Coast FIRE means you have invested enough that compound growth alone will reach your full retirement number by your target age, so you only need to cover current expenses.
How do you calculate your Coast FIRE number?
Coast number = (yearly spending ÷ withdrawal rate) ÷ (1 + real return) ^ years to retirement. $40,000 at 4% over 30 years at 5% gives about $231,377.
What return should I use?
Use a real return, after inflation, such as 4–5%. Using a nominal return with today's dollars overstates growth.
What is the FIRE number?
It is yearly retirement spending divided by the safe withdrawal rate. At 4%, $40,000 a year needs $1,000,000.
Is Coast FIRE the same as quitting work?
No. You still have to earn enough to cover your living costs until retirement; you just no longer need to save more.