About the Coast FIRE Calculator
Coast FIRE is the point where the money you already have invested will grow to your full retirement target on its own, with no further contributions. After that you only need to earn enough to cover current expenses — which is why it is popular with people who want to downshift, go part-time or take a “barista FIRE” job.
This Coast FIRE calculator works out your FIRE number from retirement spending and a safe withdrawal rate, then discounts it back to today at your real (after-inflation) return to give your Coast FIRE number. It tells you whether you have already reached it, the age at which your current savings alone would hit your FIRE number, and how much you need to save each month to reach Coast FIRE by a target age.
All figures are in today’s dollars. The calculation assumes a steady average return; real markets fluctuate, so many people add a margin of safety by using a lower return or withdrawal rate. The monthly saving figure assumes level contributions compounding monthly at the real return; if your target coast age is today and you are short, it asks for a later age instead.
With the default inputs, the coast fire number today is $329,443.28. Change any value above to recalculate instantly.
How to use the coast fire calculator
- 1Enter your current age and the age you want to fully retire.
- 2Enter the yearly spending you expect in retirement, in today’s dollars.
- 3Add how much you already have invested for retirement.
- 4Set your expected return, inflation and safe withdrawal rate.
- 5Pick the age you want to reach Coast FIRE to see the monthly saving required.
Formula and method
Your FIRE number is the portfolio that supports your yearly spending at the chosen safe withdrawal rate (25 times spending at 4%). Because the money you hold now will keep compounding until retirement, you only need the present value of that number today: divide it by one plus the real return, raised to the number of years until retirement.
Using the real return keeps everything in today’s dollars. The monthly saving figure solves for the level monthly contribution, compounding at the monthly equivalent of the real return, that brings your savings up to the Coast FIRE number required at your target coast age.
- SWR
- Safe withdrawal rate
- R
- Retirement age
- A
- Current age
- r
- Nominal annual return
- π
- Inflation rate
Worked examples
Age 30, $50k spending, $100k invested
At a 4% withdrawal rate you need $1.25 million. With a real return of about 3.88% for 35 years, that is worth about $329,000 today — so $100,000 is 30% of the way. Saving roughly $2,300 a month until 40 gets you to Coast FIRE.
Age 35, already there
A $40,000 budget needs $1 million. With a real return of about 4.85% for 30 years, the Coast number today is about $241,000, so $400,000 invested is already past it.
Frequently asked questions
What is Coast FIRE?+
Coast FIRE means you have saved enough that, with no further contributions, your investments will grow to your full retirement number by your target retirement age. You still work to pay current bills, but no longer need to save for retirement.
What is the difference between Coast FIRE and Barista FIRE?+
Coast FIRE is a savings milestone. Barista FIRE describes a lifestyle where you leave full-time work and take part-time or lower-stress work that covers expenses and often health insurance while your portfolio coasts.
Should I use a nominal or real return?+
This calculator asks for the nominal return and inflation separately and uses the real return, so every amount is in today’s dollars. That avoids understating how much you need at retirement.
What withdrawal rate should I use?+
The 4% rule comes from historical studies of 30-year retirements. Early retirees with 40–50 year horizons often use 3.25%–3.5% for a larger safety margin.
Do I really never need to contribute again?+
Only if returns match your assumption. A market crash just before retirement can leave a shortfall, so many people keep saving a little after reaching Coast FIRE or keep flexibility in their retirement date.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.