What is Coast FIRE?
Coast FIRE means your current invested assets are already large enough to grow into your retirement target without needing more contributions. You keep the money invested, let compound growth do the heavy lifting, and focus on reaching retirement without having to keep saving aggressively forever.
This calculator estimates the amount you need today to coast to your target retirement balance, the retirement balance you are aiming for, and whether your current monthly contribution is above or below the minimum needed path.
How This Calculator Works
First, it converts your spending goal into a FIRE target using your safe withdrawal rate. Then it inflates that target forward to your retirement date, because retirement income needs usually rise with inflation. After that, it discounts the target back to today using your expected annual return to estimate the Coast FIRE amount.
The chart compares your projected balance with and without contributions against your inflation-adjusted FIRE target over time.
FIRE target at retirement = FIRE target today × (1 + inflation)^years
Coast FI amount today = FIRE target at retirement ÷ (1 + return)^years
Projected balance = current assets + future contributions + compound growth
Why Coast FIRE Matters
Coast FIRE gives you a clear milestone. It shows whether your savings rate has already done enough work to let compounding carry you the rest of the way. That can change how aggressively you need to save, how you plan your career, and how you think about retirement timing.
- See how much you need today to coast
- Understand the gap between current assets and your target
- Compare projected balance with retirement spending needs
- Test different return, spending, and inflation assumptions
- Check whether your current monthly contribution is enough
How to Use This Calculator
- Enter your current age and retirement age
- Add your current invested assets
- Enter your monthly contribution
- Set your retirement spending target
- Choose a safe withdrawal rate
- Enter expected return and inflation
- Click calculate to see your Coast FIRE numbers
⚠️ Coast FIRE depends heavily on the return assumption. Be conservative if you want a safer plan.
Frequently Asked Questions
FIRE is the total amount you need to retire. Coast FIRE is the amount you need today so that your investments can reach that target later without extra contributions.
Your retirement spending target is usually stated in today's dollars. Inflation pushes that target higher over time, so the calculator adjusts it before comparing it with your portfolio.
Many people use 4% as a rough planning baseline, but a lower rate is often more conservative. The right number depends on your own risk tolerance and retirement plan.
Yes. Coast FIRE only means you do not need to keep contributing to hit the retirement target. Many people still contribute if they want a larger safety margin or earlier retirement.
Because Coast FIRE is a compounding problem. A small change in expected return can change the amount you need today by a lot, especially over long time horizons.
No. It is a planning model. Real returns, inflation, taxes, and spending needs can vary, so the result should be used as an estimate rather than a guarantee.