Formulas and 2026 figures checked & updated: July 2026
What you expect to spend per year
~7% is a common long-run stock estimate; use a lower real return for inflation-adjusted
25.0× annual expenses
Portfolio Growth to FI
How to Use the FIRE Calculator
- Enter your expected annual expenses in retirement — what you plan to spend once you stop working.
- Choose your safe withdrawal rate (4% is the classic Trinity Study figure; 3.5% is more conservative).
- The calculator multiplies expenses by the inverse of your withdrawal rate to set your FIRE number (25× expenses at 4%).
- Enter how much you currently have invested.
- Enter your monthly contribution and your expected annual investment return.
- Review your years to financial independence, plus how Lean and Fat FIRE compare at different spending levels.
- Example: $50,000/year of expenses sets a $1.25M FIRE number at the 4% rule; starting from $80,000 invested and adding $2,000/month at a 7% return reaches that number in roughly 19-20 years.
What This Calculator Does
The FIRE Calculator helps you find your 'FIRE number' — the portfolio size needed for Financial Independence, Retire Early — and shows how many years it will take to get there based on your current savings, contributions, and investment returns. FIRE is reached once your invested assets are large enough that a safe withdrawal rate can cover your living costs indefinitely, turning work from a financial necessity into a choice.
The projection is driven by five inputs: your annual expenses in retirement, how much you've already invested, your monthly contribution, your expected annual return, and your chosen safe withdrawal rate. The classic 4% rule — popularized by the Trinity Study — implies a FIRE number of 25 times annual expenses; more conservative planners often use 3.5% (about 28.5x expenses) to guard against poor early-retirement market returns, a risk known as sequence-of-returns risk. Savings rate is the single biggest driver of how fast you reach FIRE: a household saving 50% of income can realistically reach financial independence in roughly 15-17 years, while a 15% savings rate can take 40 years or more, since a higher savings rate simultaneously grows your portfolio faster and shrinks the expense base you need to cover.
This calculator is useful for anyone evaluating an aggressive early-retirement plan, deciding between Lean, regular, or Fat FIRE lifestyles, or simply testing how an extra $500/month in contributions or a lower withdrawal rate shifts their timeline. It's especially helpful when weighing trade-offs — for example, whether cutting expenses to hit Lean FIRE sooner is worth it compared to working a few more years to fund a Fat FIRE budget with more spending flexibility.
Formula
FIRE Number = Annual Expenses ÷ (Withdrawal Rate ÷ 100)At a 4% withdrawal rate this equals 25× your annual spending. The portfolio is then grown month by month until it reaches that number.
- WithdrawalSafe withdrawal rate (4% classic, 3.5% conservative)
- ReturnExpected annual investment return
- ContributionAmount invested each month
Examples
Example: $50,000 spending, 4% rule
$50,000 ÷ 0.04 = FIRE number. Start with $80,000 invested, add $2,000/month at a 7% return.
FIRE number = $1,250,000 (25× expenses). Reaching it takes roughly 19-20 years given the contributions and growth.
Example: a more conservative 3.5% rate
Same spending but withdrawing 3.5% instead of 4%.
FIRE number rises to about $1,428,000 (≈28.5× expenses), adding a few years — the price of a bigger safety margin.
Example: raising the savings rate
Same $50,000/year expense target and $80,000 starting balance and 7% return, but the monthly contribution is raised from $2,000 to $3,500.
The FIRE number stays $1,250,000, but years to independence drops from roughly 19-20 years to about 14-15 years — showing how much a higher savings rate compresses the timeline.
Key Terms Explained
- Safe Withdrawal Rate
- The share of a portfolio you can withdraw each year with low risk of running out — traditionally around 4% (the “4% rule”).
- Compound Interest
- Interest earned on both your original balance and previously earned interest, so growth accelerates the longer money stays invested.
- Real Return
- An investment's return after subtracting inflation — what your money actually gains in purchasing power.
- Inflation
- The gradual rise in prices that erodes purchasing power, so a dollar buys less over time.
Continue Your Financial Planning
Methodology
FIRE number = annual expenses ÷ (withdrawal rate ÷ 100), i.e. 25× expenses at 4%. The portfolio is projected forward monthly at your expected return plus contributions until it crosses the FIRE number. Returns are nominal; for an inflation-adjusted view, enter a real (after-inflation) return.
Frequently Asked Questions
What is a FIRE number?+
The portfolio size where a safe withdrawal rate covers your spending. At 4%, that's 25× annual expenses — $40,000 of spending needs $1,000,000. A 3.5% rate (≈28.5×) is more conservative.
What is the 4% rule?+
Based on the Trinity Study: withdraw 4% the first year, adjust for inflation after, with high odds the money lasts 30+ years. It's a guideline, not a guarantee — sequence risk and long retirements may justify a lower rate.
Lean vs. regular vs. Fat FIRE?+
Lean FIRE = frugal budget and a smaller portfolio; regular FIRE = typical middle-class spending; Fat FIRE = higher spending and a much bigger portfolio. Same 4% math, different expense figure.
How does savings rate affect my FIRE date?+
It's the biggest lever — saving 50% of income can reach FI in ~15-17 years, while 15% can take 40+. A higher savings rate grows the portfolio faster and lowers the expenses you must cover.
Does the FIRE number account for inflation?+
The FIRE number is expressed in today's dollars, and the 4% rule already builds in an annual inflation adjustment to your withdrawals so your purchasing power stays roughly steady over time. If you enter a nominal (not inflation-adjusted) expected return, your projected years-to-FI will look faster than it would in real terms, since part of that growth is just inflation. For a more conservative projection, use a real return — typically 2-3 percentage points lower than the nominal figure.
What is Coast FIRE?+
Coast FIRE is the point where your current invested balance is large enough to grow, through compounding alone with no further contributions, into your full FIRE number by a traditional retirement age. Once you hit Coast FIRE, you only need to earn enough to cover current living expenses, since your existing investments will 'coast' to the finish line on their own.
Is FIRE realistic on an average income?+
Reaching FIRE is mathematically possible at almost any income level because the key driver is savings rate, not income size, but a higher income makes it far easier to save 30-50% without drastically cutting spending. On a median income, FIRE is achievable but typically requires a higher savings rate, a lower-cost lifestyle, or a longer accumulation period than someone with a six-figure income pursuing the same target.
Can I save my results?+
Yes. Use “Save results” to store a snapshot. Without an account it remains in this browser. If you log in, saved scenarios sync securely to your SmartRates account so they are available on your other devices.
How do I share my calculation?+
Click “Share” in the toolbar to copy a link (or open your device’s share sheet). The link encodes your exact inputs, so whoever opens it sees the calculator pre-filled with the same numbers and the same result.
Can I email my calculator results?+
Yes. Click “Email results” to open your default email application with the current inputs, results, and calculator link already included. Review the message and choose the recipient before sending.
Can I export or print my results as a PDF?+
Yes. Click “Export PDF” to open a clean, printable summary of your inputs and results that you can save as a PDF or print. It includes a timestamp and a link back to the calculator.
How accurate are the calculator results?+
The arithmetic follows the formula and assumptions documented on this page. The result is still an estimate because actual rates, fees, taxes, timing conventions, eligibility rules, and provider calculations can differ. Use figures from your official quote, statement, contract, or tax form before making a financial decision.
Which inputs have the biggest effect on the result?+
Rate, time, starting balance, recurring payments or contributions, and fees usually have the largest effects. Change one input at a time to create a conservative, expected, and optimistic scenario instead of relying on a single forecast.
Are taxes, fees, and inflation included?+
Only when they appear as an input or are explicitly described in the methodology. Do not assume an omitted cost is zero. Review the formula and methodology sections to see exactly what is included before comparing the result with an outside quote.
Can this calculator predict future rates or returns?+
No. A calculator projects the assumptions entered; it cannot predict market returns, inflation, variable interest rates, tax-law changes, or provider decisions. Rerun the calculation with several assumptions to understand the range of possible outcomes.
Why might my lender, bank, broker, or tax software show a different result?+
Professional systems may use daily timing, transaction dates, compounding conventions, rounding rules, account-specific fees, credits, eligibility details, or regulations that a general-purpose calculator cannot know. A small difference can be rounding; a large difference usually means an assumption or included cost is different.
Disclaimer: Calculations are for informational purposes only and do not constitute professional financial advice. Please consult with a certified professional before making financial decisions.