Coast FIRE Calculator
Coast FIRE is the retirement milestone where your invested nest egg is large enough that — left alone with zero further contributions — it will compound to full financial independence by traditional retirement age (typically 65). Calculate your personal Coast FIRE number using the 4% safe withdrawal rule and real (inflation-adjusted) returns.
What Is Coast FIRE?
Coast FIRE (Financial Independence, Retire Early — Coasting variant) is a savings milestone where your current invested portfolio is large enough that, left alone with no further contributions, it will compound to full retirement by traditional retirement age (typically 65). Once you reach Coast FIRE, you can stop contributing to retirement accounts and still retire comfortably at 65. You can "coast" — earning just enough to cover current living expenses while your invested capital does the heavy lifting through compounding. Per Bogleheads community FIRE resources, Coast FIRE is the most achievable FIRE variant because it doesn't require massive ongoing savings — just one significant nest egg early in your career, then time. Last updated May 2026.
The Coast FIRE Formula
Coast FIRE Number = Full FIRE Number ÷ (1 + real return)^years to retirement. Full FIRE Number = Annual Spending ÷ Safe Withdrawal Rate (typically 4% per the Trinity Study and Kitces' updated analyses). Example: a 32-year-old with $50,000/year retirement spending needs $1.25M at age 65 (Full FIRE). Discounted back 33 years at 5% real return, today's Coast FIRE number is about $246,000. Reaching $246,000 invested at 32 — then never adding another dollar — means $1.25M waiting at 65 (in today's purchasing power). The earlier you reach Coast FIRE, the more years of compounding work for you and the smaller the required amount.
Why Coast FIRE Beats Full FIRE for Most People
Full FIRE (saving aggressively until you can retire at 40-50) requires extreme savings rates of 50-70% of income for 15-20 years. Coast FIRE requires high savings for only 5-10 years until you hit the milestone, then near-zero retirement savings for 30+ years. The total dollars saved are dramatically lower for Coast FIRE because you let the market compound the gap. Coast FIRE also leaves room for career changes, sabbaticals, or part-time work without derailing the plan — once invested, the nest egg doesn't care if you take time off. Per Kitces' financial planning research, this flexibility is the biggest psychological win of Coast FIRE versus traditional retirement planning or full FIRE.
Real Return Assumptions and the 4% Rule
The 4% safe withdrawal rate comes from the original 1998 Trinity Study (Cooley, Hubbard, Walz) and has been re-validated by Bengen, Pfau, and others. Real return assumption matters: 5% real (after-inflation) is the consensus for a balanced 60/40 stock/bond portfolio. Aggressive 100% equity portfolios have averaged ~7% real over very long periods (per S&P Dow Jones Indices historical data), but with much higher short-term volatility. Conservative portfolios with significant bonds average 4% real. The calculator lets you pick your assumed return — be honest about your true risk tolerance. Source: Trinity Study (Cooley/Hubbard/Walz), Wade Pfau retirement income research, Bogleheads forum FIRE wiki.