FIRE (Financial Independence, Retire Early) calculator based on the 4% safe-withdrawal rate from the Trinity Study.
Four tabs: FIRE number (LeanFIRE / FIRE / FatFIRE), years to FIRE, savings-rate impact, and Coast FIRE (investment needed today to retire without further contributions).
Disclaimer: Historical investment returns do not guarantee future results. Consult a fee-only financial planner.
Calculator information
📋 How to use this calculator
- Select the FIRE Number tab and enter your target annual retirement spending (for example, $40,000/year for a frugal lifestyle).
- The calculator applies the rule of 25 (= 25x annual spending) for LeanFIRE, FIRE, and FatFIRE - LeanFIRE for minimal spending, FatFIRE for a high-spending lifestyle.
- Years to FIRE tab: enter current net worth, monthly investment contributions, and an assumed annual return (7-10% for a diversified equity portfolio); the tool returns years to FI.
- Savings Rate Impact tab: compare savings rates (10/25/50/70%) and years to FIRE - ranging from 51 years (10%) down to 8.5 years (70%).
- Coast FIRE tab: calculate how much invested today will grow on its own (no further contributions) to fund retirement at age 65 - useful for those who want to dial back career intensity.
- Use an inflation assumption of 2-3% for the US to keep real returns realistic (CPI averaged 2.5% over the past 30 years).
🧮 FIRE Number, Trinity Study 4% Rule, and Time to FI
FIRE_Number = Annual_Spending x 25; Years_to_FI = log(FIRE_Number / Current_Net_Worth) / log(1 + (Savings_Rate / (1 - Savings_Rate)) x return + return)
- Annual_Spending = total target cost of living in retirement (USD/year)
- 25 = the inverse of the 4% safe withdrawal rate (Trinity Study, Bengen 1994)
- Current_Net_Worth = total liquid investable assets
- return = real return after inflation (typically 5-7% for a diversified equity portfolio)
- Savings_Rate = percentage of take-home pay saved and invested
The Trinity Study (1998) modeled 60/40 stock/bond portfolios over 30-year rolling periods from 1925-1995 and found that a 4% inflation-adjusted withdrawal rate had a roughly 95% success rate. FIRE tiers: LeanFIRE under $40k/year, regular FIRE $40-100k/year, FatFIRE above $100k/year. Coast FIRE means stopping contributions and letting compounding do the rest.
💡 Worked example: A 30-year-old professional aiming for FI at 45 (15 years)
Given:- Current net worth: $50,000 (mix of 401(k), Roth IRA, and taxable brokerage)
- Target annual retirement spending: $60,000 (comfortable middle-class lifestyle)
- Monthly contribution: $2,000/month = $24,000/year
- Assumed real return: 7% per year
Steps:- FIRE Number = $60,000 x 25 = $1.5 million
- Future value of $50,000 over 15 years at 7% = $50,000 x 1.07^15 = $137,950
- Future value of $24,000/year over 15 years (annuity) = 24,000 x [(1.07^15 - 1)/0.07] = $603,000
- Total projected balance in year 15 = $137,950 + $603,000 = $741,000
- Shortfall of $759,000 vs FIRE Number - needs an extra 5-6 years, or raise contributions to ~$4,500/month
Result: At $2,000/month, FI lands around age 51; about $4,500/month is needed to hit the target at 45.
❓ Frequently asked questions
Does the 4% rule still hold today?
The Trinity Study used US market data with average inflation of about 3%. Modern updates (Wade Pfau, Big ERN) suggest 3.25-3.5% is safer for early retirees with 40-50 year horizons, especially given today's higher equity valuations and lower bond yields. The 4% rule remains a useful planning baseline; a 3.5% rate provides a margin for sequence-of-returns risk. Global diversification (US + international equities) helps reduce country-specific risk.
What savings rate gets to FIRE in 10 years?
Per Mr. Money Mustache's math at a 5% real return, a 65% savings rate gets to FIRE in 10.5 years, 70% in 8.5 years, and 75% in 7 years. For a US household earning $120,000 take-home, a 65% savings rate means investing $78,000/year while living on $42,000. Challenging but achievable with low housing costs, no car loans, and disciplined spending.
What is the difference between LeanFIRE, FIRE, and FatFIRE?
LeanFIRE (~$500K-1M portfolio, spending under $40K/year): minimalist living, small home or geoarbitrage to a low-cost-of-living area, no kids or modest family size. Regular FIRE ($1M-2.5M, spending $40K-100K/year): comfortable middle-class life. FatFIRE (over $2.5M, spending above $100K/year): high-end lifestyle with travel, premium housing, and private school for kids.
What is Coast FIRE?
Coast FIRE is the amount invested today that, left to compound with no further contributions, will grow to your FIRE Number by traditional retirement age (say 65). Example: targeting $1.5M at age 65 from age 30, at 7% real return, you need $1.5M / 1.07^35 = $140,500 today. Once you hit Coast FIRE, you only need to earn enough to cover current living expenses - the long-term retirement piece is handled.
Is early retirement realistic in the US?
Yes, and the US has strong structural advantages: tax-advantaged accounts (401(k), Roth IRA, HSA), the Roth conversion ladder for accessing pre-tax money before 59 1/2, and ACA subsidies that make pre-Medicare health insurance affordable for early retirees with low taxable income. Key strategies: maximize 401(k) and IRA contributions, use a brokerage account for bridge funds, and plan for healthcare via ACA marketplace plans until Medicare eligibility at 65.
📚 Sources & references
Last updated: May 11, 2026