Coast FIRE Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: August 20, 2026The Point Where You Can Stop Contributing and Still Get There
Coast FIRE marks the moment your existing savings, left alone with no further contributions, will grow through compounding alone into a full FIRE number by your target retirement age. Reach that point and you're free to cover only current living expenses — through a lower-stress job, part-time work, or a career break — without derailing eventual financial independence. This calculator works out how much that "coast point" balance actually is at your current age.
The Formula
Coast FIRE Number = FIRE Number ÷ (1 + r)years
The Coast FIRE number is simply the FIRE number discounted backward from retirement age to today at your expected annual return — the present value needed for compounding alone to finish the job.
Where This Calculation Matters
- Deciding to downshift careers — once you've coasted, additional income only needs to cover today's expenses, not retirement savings too.
- Evaluating a sabbatical or lower-paying passion job — knowing your coast number tells you whether pausing contributions now still leaves retirement on track.
- Early aggressive saving strategies — because the coast number shrinks the more time compounding has to work, reaching it early (in your 20s or 30s) requires a much smaller balance than reaching it in your 40s or 50s.
- Milestone-based motivation — coast FIRE gives a concrete, earlier target than full FIRE, which can be motivating for long-horizon savers.
Coast FIRE Number by Current Age
| Current age | Years to grow | Coast FIRE number needed today |
|---|---|---|
| 25 | 40 | $100,170.57 |
| 30 | 35 | $140,494.41 |
| 35 | 30 | $197,050.68 |
| 40 | 25 | $276,373.77 |
| 45 | 20 | $387,628.50 |
| 50 | 15 | $543,669.03 |
| 55 | 10 | $762,523.94 |
The required balance roughly doubles for every 10-11 years less time compounding has to work at a 7% return.
How to Use This Calculator
- Enter your current age and planned retirement age.
- Enter your current investable savings.
- Enter your expected annual expenses in retirement.
- Enter your expected annual return rate.
- Enter your target withdrawal rate, or leave the 4% default.
- Select Calculate to see your Coast FIRE number and whether your current savings have already reached it.
Related Calculations
See the full contribution-driven path with the FIRE Calculator, or model continued part-time income after coasting with the Barista FIRE Calculator.
Principles of Coast FIRE (Compound Growth Early Retirement Milestones)
A Coast FIRE calculator computes the exact lump-sum investment portfolio required today such that, with ZERO additional lifetime savings contributions, compound investment growth alone will expand the portfolio to full financial independence by traditional retirement age (Age 60 to 67). Reaching Coast FIRE liberates workers to quit high-stress jobs and pursue lower-paying passion careers that merely cover basic daily living expenses.
The Fundamental Coast FIRE Formula
Where Target Full FIRE Number = Annual Retirement Expenses × 25
rreal = Real inflation-adjusted annual investment return (typically 5.0% to 7.0%)
t = Years remaining until target retirement age (Retirement Age - Current Age)
Coast FIRE Strategic Advantages
| Financial Dimension | Traditional Retirement Path | Coast FIRE Strategy |
|---|---|---|
| Ongoing Savings Requirement | Must save 15% to 25% of salary every single year until age 65 | $0.00 Required Savings! (Earn only enough to cover rent/food) |
| Career Flexibility | Locked into high-paying corporate roles to maximize savings | Freedom to take freelance work, non-profit roles, or part-time consulting |
| Compound Interest Leverage | Late-career contributions do very little compound work | Front-loads investments in 20s/30s — 30+ years of compounding |
Step-by-Step Worked Calculation Example
Example: Calculating Coast FIRE Milestone for a 30-Year-Old
Problem: A 30-year-old worker plans to fully retire at Age 65 (t = 35 years of growth). Desired retirement living expenses = $60,000/year (Full FIRE Target = $60,000 × 25 = $1,500,000). Assumed inflation-adjusted real stock market return = 6.0%. Calculate the worker's exact Coast FIRE target today.
Step 1: Calculate Compound Growth Multiplier over 35 Years:
Multiplier = ( 1 + 0.06 )35 = ( 1.06 )35 = 7.6861
Step 2: Compute Coast FIRE Target Today:
Coast FIRE Number = $1,500,000 / 7.6861 = $195,157.50
Conclusion: Once this 30-year-old accumulates $195,158 in index funds, they can stop saving for retirement forever — compounding alone grows the balance to $1.5M by age 65.
Real vs. Nominal Return Sensitivity in Coast FIRE Modeling
Coast FIRE calculations are extraordinarily sensitive to long-term Real Inflation-Adjusted Return Assumptions:
| Real Return Assumption | 30-Year Compounding Multiplier (1+r)30 | Required Coast FIRE for $1.5M Goal |
|---|---|---|
| 4.0% Real Return (Ultra-Conservative) | 3.24x | $462,480.00 |
| 5.0% Real Return (Conservative) | 4.32x | $347,065.00 |
| 6.0% Real Return (Standard S&P 500 Real) | 5.74x | $261,160.00 |
| 7.0% Real Return (Historical Equity Real) | 7.61x | $197,050.00 |
Geographic Arbitrage (Geo-Arbitrage)
Pairing Coast FIRE with Geo-Arbitrage (relocating from high-cost metros like NYC or San Francisco to low-cost states or international hubs) slashes living expenses by 40%, reducing required Coast FIRE capital from $260k down to under $150,000.
Coast FIRE for Parents: Funding Children's College 529s
The Coast FIRE methodology applies identically to higher education savings.
Investing $20,000 into a state 529 College Savings Plan at a child's birth compounds at an 8.0% nominal return over 18 years to reach over $80,000 in 100% tax-free college tuition funding, allowing parents to "Coast" on college savings throughout the child's school years.
Downshifting Careers: The "Mini-Retirement" Paradigm
Reaching Coast FIRE unlocks the psychological freedom to take extended 6 to 12-Month Sabbaticals ("Mini-Retirements") every 5 to 7 years throughout one's 30s and 40s.
Because compound investment interest continues expanding the baseline retirement nest egg in the background, sabbaticals require only saving a temporary cash buffer to cover living expenses during the time away from active work.
Coast FIRE and Psychological Freedom from Burnout
The greatest return on investment of Coast FIRE is immediate psychological relief.
Knowing your traditional retirement is 100% mathematically funded in the background eliminates corporate career anxiety, empowering employees to decline mandatory overtime, negotiate remote work arrangements, or take parental leave without sacrificing long-term financial security.
Coast FIRE and Social Security Windfalls
Most conservative Coast FIRE calculations assume $0 in future government Social Security retirement benefits.
Factoring in even a modest 70% Social Security benefit payout starting at Age 67 provides a massive financial safety net, offsetting late-life medical expenses and market downturns.
Rebalancing Asset Allocations During the Coast Phase
Because Coast FIRE investors make zero new capital contributions, portfolio asset allocation drift can occur during bull markets; scheduling an annual automatic portfolio rebalance maintains optimal 80/20 equity-to-bond risk targets.
Coast FIRE and Debt Freedom Milestones
Eliminating high-interest consumer debt before declaring Coast FIRE lowers annual baseline living expenses, permanently compressing the total investment target needed for full retirement security.