How Much Do I Need?
Calculate your FIRE number and explore different retirement strategies — from Lean to Fat FIRE.
This is where every FIRE journey starts: figuring out your number. Whether you're aiming for Lean FIRE on a minimalist budget or Fat FIRE with no compromises, these calculators turn your income, expenses, and goals into a concrete target. All estimates use the 4% rule methodology backed by the Trinity Study.
Every FIRE journey starts with the same question: how much do I actually need? Not "how much can I save" — that's a separate question. The foundational question is: what portfolio size lets you stop working and live off your investments? For most people, the answer comes down to one of four targets — Lean FIRE ($500K-$750K), Standard FIRE ($1M-$1.25M), Fat FIRE ($2.5M+), or Coast FIRE (a milestone you hit on the way to any of the above). The differences are dramatic: Lean FIRE requires roughly one-sixth the portfolio of Fat FIRE, and the trade-offs are real but manageable.
The math behind these targets is the 4% rule: if you can live on 4% of your portfolio annually, your money lasts 30+ years with a 95% historical success rate. This gives us the canonical formula — FIRE Number = Annual Expenses × 25. For someone spending $40,000/year, the target is $1,000,000. For $60,000/year, it's $1,500,000. The 25x multiplier isn't magic; it's the inverse of the safe withdrawal rate.
These calculators take the guesswork out of the FIRE number. They handle the different strategies (Lean, Standard, Fat, Coast, Barista, Couple), adjust for country-specific cost of living and tax rates, and project timelines from your current age and savings rate.
Lean vs Standard vs Fat: choosing your number
The four primary FIRE strategies differ primarily by lifestyle ambition, not by math sophistication. Lean FIRE targets a minimalist budget — typically $20,000-$40,000/year for an individual or $40,000-$60,000 for a couple. At $30,000/year, your FIRE number is $750,000. Lean FIRE trades material comfort for earlier freedom and is most popular with frugal-living enthusiasts and geographic arbitrageurs who plan to live in low-cost areas. Standard FIRE targets a comfortable middle-class lifestyle — $50,000-$80,000/year for most Americans, with a FIRE number around $1.25M-$2M. Fat FIRE targets $100,000+/year — luxurious travel, premium healthcare, suburban home — with FIRE numbers of $2.5M-$5M+.
The "right" strategy depends on three things: (1) what lifestyle genuinely makes you happy, (2) what expenses are truly fixed vs discretionary, and (3) how long you're willing to work. Most FIRE planners under-spend in accumulation and gradually increase spending in retirement — what ChooseFI calls "F-you money" — rather than locking in a fixed number at the start. The Coast FIRE Calculator is useful here: it tells you the age at which you can stop saving entirely and let compounding do the rest.
How accurate is the 25x rule?
The 25x rule comes from the Trinity Study (Cooley, Hubbard, Walz, 1998, updated 2011), which analyzed US stock and bond returns from 1926-1995. The study found that a 4% initial withdrawal rate, adjusted for inflation annually, sustained a 30-year retirement in 95% of historical scenarios. The 25x multiplier is just 1 ÷ 0.04 — not a magic constant but a translation of the safe withdrawal rate.
But the 25x rule has caveats for FIRE investors. First, it was designed for 30-year retirements, not 50-year ones. Early retirees at 40 face a 60+ year horizon, and the historical success rate drops. Most FIRE planners target a 3.25-3.5% withdrawal rate (28x-31x multiplier) for added safety. Second, the study assumed a 50-75% stock allocation; more conservative portfolios may need lower WRs. Third, 2026's elevated CAPE ratio (~38) suggests current valuations are higher than historical norms, which historically corresponds to lower future returns. Use the Safe Withdrawal Rate Calculator to stress-test your specific scenario.
When your FIRE number changes
Your FIRE number isn't a one-time calculation — it shifts with life events. Getting married or divorced typically changes expenses by 30-50% (shared housing, healthcare, lifestyle). Having children adds $10,000-$25,000/year per child (childcare, food, healthcare, education, activities). Buying a home in cash adds to your number; a mortgage adds ongoing expenses. Health events — chronic conditions, aging parents needing support, ACA subsidy changes post-65 — can shift expenses 10-30%.
Geographic moves are the most powerful lever: moving from a high-cost area (San Francisco, NYC) to a low-cost area (Cincinnati, Pittsburgh) can cut your expenses by 30-50%, dropping your FIRE number proportionally. International moves (Mexico, Portugal, Thailand) can cut further. The Cost of Living Calculator and the country-specific FIRE Number Calculators (USA, UK, Japan, India, etc.) make this concrete.
The FIRE With Kids Calculator and Couple FIRE Calculator handle the most common life-stage transitions. Most FIRE planners recalculate their number every 1-2 years or after major life events, not because the math changes but because life does.
A practical FIRE number framework: start with a baseline annual expense estimate using current actual spending (not aspirational future spending). Most planners find their baseline is 10-20% higher than they expected because subscriptions, dining, and lifestyle creep add up. Then add buffers — 10% for healthcare volatility pre-65, 5% for tax law changes, 10% for unexpected long-term care needs. The result is rarely the clean "expenses × 25" target — it's more like expenses × 27-30 to account for the real-world buffers every FIRE retiree eventually needs.
For couples planning together, the framework is the same but the math divides differently. Combined expenses run 50-80% higher than a single person's (not 2x) because housing, utilities, and many fixed costs are shared. Each partner's Social Security benefit (delayed to 70) and any pensions add $30,000-$60,000/year to retirement income, effectively reducing the required portfolio by $750,000-$1.5M at a 4% withdrawal rate. The Couple FIRE Calculator captures these multi-person dynamics that single-person FIRE calculators miss.
The Can I FIRE Calculator answers the most common variant of the question: given your current age, savings, income, and spending, what age can you actually FIRE? It runs a year-by-year projection with realistic return assumptions and shows whether your current trajectory hits your FIRE number — or whether you need to adjust savings rate, retirement age, or expected spending.
Finally, remember that the FIRE number is a moving target, not a finish line. Many retirees reach their original number and continue working because they enjoy their career, then pull back to Barista FIRE or Coast FIRE rather than full stop. Others hit their number early and discover that the lifestyle they can afford at $40K/year is plenty satisfying — they lean FIRE and pursue other goals. The calculators below help you find your number, but the lifestyle design around that number is yours.
Key Takeaways
- FIRE Number = Annual Expenses × 25 at the standard 4% safe withdrawal rate
- Lean FIRE vs Fat FIRE differ by roughly 6x portfolio size for the same person
- Coast FIRE is the middle path: stop saving early, let compounding do the rest
- Country-specific FIRE numbers vary 30-60% due to cost of living and tax structure
- For 40+ year retirements, target a 3.25-3.5% safe withdrawal rate (28x-31x multiplier) instead of 4%
If you're just starting your FIRE journey, begin with the FIRE Number Calculator. Already have a number? Explore Coast FIRE to find your coast number, or Barista FIRE if you want a semi-retirement path.
All 26 Calculators in This Category
Frequently Asked Questions About How Much Do I Need?
What is a FIRE number?
Your FIRE number = annual expenses × 25. This is based on the 4% withdrawal rule: you can safely withdraw 4% of your portfolio each year without running out of money over a 30-year retirement (Trinity Study, Bengen 1994). For someone spending $40,000/year, the FIRE number is $1,000,000. Use the FIRE Number Calculator for a personalized result.
Which FIRE strategy is right for me?
Start with the Standard FIRE Number Calculator for your baseline. Lean FIRE targets a minimalist budget ($20K-30K/year) with a 6-9 year timeline to FI. Fat FIRE maintains a higher-spending lifestyle ($100K+/year) but requires more aggressive saving. Coast FIRE lets you stop saving early while your portfolio grows. Barista FIRE combines part-time work with portfolio withdrawals for semi-retirement.
Do these calculators work for non-US investors?
Yes. We have country-specific FIRE number calculators for 20 countries with local currency, cost-of-living adjustments, and country-specific tax considerations. Each adjusts the 4% rule for local market conditions and retirement account structure (ISA in UK, TFSA in Canada, NISA in Japan, etc.).
Should I include my home equity in my FIRE number?
Generally no — your primary residence is not part of your investable portfolio. The 4% rule applies to assets you can draw from annually. However, paid-off housing does reduce your required annual expenses (no rent/mortgage), which lowers your FIRE number. Downsizing or a reverse mortgage are options for accessing home equity in retirement.
How does FIRE work for couples vs single people?
Couples typically share housing, utilities, and many fixed costs, so expenses don't double. A couple spending $60,000/year combined has a FIRE number of $1,500,000 — only 50% more than a single person at $40,000/year. The Couple FIRE Calculator handles two Social Security benefits, joint expenses, and survivor scenarios.
What healthcare costs should I budget before Medicare at 65?
ACA marketplace premiums for a 40-50 year old are typically $400-$1,200/month for a mid-range plan, plus out-of-pocket costs. Budget $8,000-$18,000/year for healthcare before 65. After 65, Medicare + supplemental plans run $5,000-$10,000/year. The FIRE With Kids Calculator and Cost of Living Calculator include healthcare line items.
How do children affect my FIRE number?
Each child adds roughly $10,000-$25,000/year to expenses through ages 0-18, plus college costs (~$25,000/year × 4 years at public in-state, more for private). A family with 2 kids needs a FIRE number roughly $400,000-$1M larger than a childless couple with similar baseline spending. Use the FIRE With Kids Calculator to model.
What return rate should I assume for FIRE planning?
Use 7% nominal (4% real after 3% inflation) as the standard assumption for a 60-80% stock allocation. Historical US stock returns average 10% nominal (7% real), but future returns may be lower. The FIRE Number Calculator defaults to 7% and lets you stress test with 5%, 6%, 8% returns. Conservative planners use 4-5% real.
Where does the 25x rule come from?
The 25x rule is the inverse of the 4% safe withdrawal rate established by the Trinity Study (Cooley, Hubbard, Walz 1998). The study analyzed 30-year retirements from 1926-1995 and found 4% initial withdrawal, adjusted for inflation, succeeded in 95% of historical scenarios. The Bengen 1994 paper is the original source.
Should I use 3% or 4% for a 40+ year FIRE retirement?
For FIRE retirements of 40+ years (retiring at 40 instead of 65), most experts recommend 3.25-3.5% (28x-31x multiplier). The original Trinity Study tested 30-year retirements. Early retirees face sequence-of-returns risk over a longer horizon, so a more conservative withdrawal rate provides safety margin. The Safe Withdrawal Rate Calculator stress-tests both rates against historical data.