Free calculator
Coast FIRE Calculator
Estimate whether today's invested retirement savings could compound to your target by retirement without another contribution.
Reviewed September 3, 2026
Short answer
Coast FIRE is a savings milestone, not a retirement-readiness verdict. In the example below, a 40-year-old targeting age 65 needs about $482,000 invested today to reach a $1.25 million target in today's dollars without new contributions.
Social Security, pension, or other dependable income
You are $17,779 above this Coast FIRE number.
This uses a 3.9% real return for 25 years. It assumes no new contributions and a steady return, so it is a milestone, not a retirement-readiness verdict.
Uses a constant annual return, constant inflation, and the withdrawal rate you choose. Results are shown in today’s dollars and assume no new contributions. No return or withdrawal rate is guaranteed.
This is an educational estimate, not tax or financial advice. Figures reflect the law year shown and the inputs you provide. Consult a qualified professional before acting.
Sources
- Compound Interest Calculator — U.S. Securities and Exchange Commission
The future-value compounding relationship used to carry today's portfolio to retirement age.
Accessed September 3, 2026
- Determining Withdrawal Rates Using Historical Data — Journal of Financial Planning
Why a withdrawal rate is an assumption grounded in historical sequences, not a guaranteed safe rate.
Accessed September 3, 2026
How it’s calculated
- Subtract dependable retirement income from annual retirement spending, then divide the remaining portfolio-funded spending by your chosen withdrawal rate.
- Convert the expected return to a real return after inflation: (1 + return) ÷ (1 + inflation) − 1.
- Discount the retirement portfolio target back by the years until retirement. That is the Coast FIRE number today.
- Compare today's invested retirement savings with that number. No future contributions are assumed.
Worked Coast FIRE example
- Current age
- 40
- Retirement age
- 65
- Invested today
- $500,000
- Portfolio-funded spending
- $50,000/year
- Return / inflation
- 7% / 3%
- Withdrawal rate
- 4%
Result
About $482,000 needed today; $500,000 is roughly $18,000 above the Coast FIRE number.
The $50,000 annual portfolio need implies a $1.25 million retirement target at 4%. Discounting that target for 25 years at the inflation-adjusted return produces today's Coast FIRE number.
What this calculator does not cover
- A steady return hides market volatility and sequence risk.
- Taxes, investment fees, healthcare changes, and account-specific withdrawal treatment are not modeled.
- The withdrawal rate is an input, not a promise that a portfolio will last.
- Dependable income is treated as one annual amount rather than starting at different ages.
Frequently asked
- Is a Coast FIRE number the same as a retirement target?
- No. The retirement target is the portfolio needed at retirement. The Coast FIRE number discounts that target back to today using the selected real return and years remaining.
- Does the Coast FIRE calculation include future contributions?
- No. By definition this calculation asks whether the current invested portfolio could reach the target without another contribution. Continuing to save creates additional margin.
- Can I retire when I reach Coast FIRE?
- Not necessarily. Coast FIRE assumes you still earn enough to cover spending before the retirement age you selected. It is an accumulation milestone, not a current retirement-readiness result.