A fire number calculator answers the one question every aspiring early retiree asks: how much is enough? Someone earning $70,000 a year and saving 10% of it will work for over 50 years before reaching financial independence. Bump that savings rate to 50%, and the timeline drops to 17 years. Same income. Same city. Same job.
The gap between those two outcomes — 33 years of your life — comes down to a single number.
Your FIRE number.
FIRE stands for Financial Independence, Retire Early. The FIRE number is the exact dollar amount you need invested before work becomes optional. Most people guess their way there. The math is more precise — and more surprising — than you’d expect.
Calculate Your FIRE Number
Before the math lesson — try it yourself. This FIRE number calculator takes your annual expenses, current savings, and expected return, then handles the compounding.
💡 How to Use This Calculator
- 1. Annual Expenses — total yearly spending (rent, food, insurance, everything).
- 2. Current Savings — total invested assets (401k, IRA, brokerage).
- 3. Monthly Savings — how much you invest each month going forward.
- 4. Expected Return — S&P 500 averages ~10%. Use 7–8% for conservative.
- 5. Withdrawal Rate — 4% is the standard from the Trinity Study.
If the result looks intimidating, good. That reaction is normal. But the gap between where you are and where you need to be shrinks faster than most people expect — compound growth accelerates the second half of every timeline.
The Formula Behind Every FIRE Number
One equation runs the entire movement:
FIRE Number = Annual Expenses × 25
Spend $40,000 a year? Your target is $1,000,000. Spend $60,000? You need $1,500,000. Spend $100,000? That’s $2,500,000.
The “× 25” multiplier comes from the 4% rule — a withdrawal rate derived from the Trinity Study, which analyzed 75 years of U.S. market data. A retiree withdrawing 4% annually, adjusted for inflation, had a 95%+ success rate over 30-year periods with a balanced stock-bond portfolio.
Flip 4% upside down: 1 ÷ 0.04 = 25. That’s where the multiplier comes from.
I used to think $1 million was an arbitrary “rich person” target. It’s not. For someone spending $40K a year, it’s the mathematical threshold where investment returns replace earned income.
Savings Rate — The Only Lever That Moves the Needle
Income gets all the attention. Savings rate does all the work. The FIRE number calculator above demonstrates this directly — try changing only the savings rate and watch the timeline shift.
A household earning $200,000 but spending $180,000 has a 10% savings rate — and roughly a 51-year path to independence. Another household earning $80,000 but spending $40,000 has a 50% savings rate and reaches the same milestone in 17 years. The family earning less gets there 34 years sooner.
Read that again.
| Savings Rate | Years to FIRE | FIRE Number ($60K Spend) |
|---|---|---|
| 10% | 51 years | $1,500,000 |
| 20% | 37 years | $1,500,000 |
| 30% | 28 years | $1,500,000 |
| 50% | 17 years | $1,500,000 |
| 60% | 12.5 years | $1,500,000 |
| 70% | 8.5 years | $1,500,000 |
Assumptions: 7% real (inflation-adjusted) annual return, starting from $0 savings. Model consistent with historical S&P 500 backtests and the framework popularized by the FIRE community.
Notice something? The FIRE number stays the same across every row. $1,500,000. It depends on expenses, not income. Your savings rate only changes how fast you get there.
Five Types of FIRE — and Their Target Ranges
FIRE isn’t one strategy. The community has split into distinct approaches, each with different lifestyle assumptions.
Most FIRE number calculators default to the standard 25× multiplier. Fat FIRE planners sometimes use 33× (a 3% withdrawal rate) for an extra safety margin against prolonged bear markets. Both are mathematically valid — the choice depends on how much cushion you want.
Why the 4% Rule Isn’t Bulletproof — And What to Do About It
The Trinity Study analyzed 30-year retirement windows. If you’re planning to quit at 35, your money needs to last 50–60 years. That changes the calculus.
Big ERN (Early Retirement Now) published a 60+ part safe withdrawal rate series using data from 1926 to present. The key finding for early retirees: a 3.25%–3.5% withdrawal rate historically showed higher survival rates than 4% over very long horizons.
Does that mean 4% is broken? Not for most scenarios. The 4% rule remains effective — especially for people willing to flex. Cutting spending by 10–15% during a bear market dramatically improves long-term portfolio survival. Rigidity is the real risk, not the withdrawal percentage.
Three Scenarios: Same Income, Different Timelines
All three earn $90,000 a year. Run each scenario through the FIRE number calculator and watch how spending choices reshape the path.
| Alex | Jordan | Morgan | |
|---|---|---|---|
| Gross Income | $90,000 | $90,000 | $90,000 |
| Annual Spending | $72,000 | $54,000 | $36,000 |
| Savings Rate | 20% | 40% | 60% |
| FIRE Number (25×) | $1,800,000 | $1,350,000 | $900,000 |
| Years to FIRE | ~37 years | ~22 years | ~12.5 years |
Morgan’s advantage is double-edged. Spending less means a lower FIRE number and faster accumulation speed. The math rewards frugality twice.
What Most FIRE Number Calculators Miss
A FIRE number calculator gives you a starting point — not a finish line. Four variables can shift your real target by six figures.
Your Three-Step FIRE Action Plan
Knowing the number is step one. Closing the gap takes three moves — in this order.
Your FIRE number tells you where to go. Your savings rate decides when you arrive. The difference between a 20% and 50% savings rate isn’t a lifestyle sacrifice — it’s 15+ years of your working life.
The 4% rule isn’t a guarantee. But paired with flexibility, diversification, and honest expense tracking, it remains the most battle-tested framework for financial independence. Run the FIRE number calculator above. Then start closing the gap.
Frequently Asked Questions
What is a good FIRE number for a 30-year-old?
It depends on annual expenses, not age. Use the FIRE number calculator above with your real spending. A 30-year-old spending $50,000/year would target $1,250,000 (25× expenses). Someone spending $80,000 would aim for $2,000,000. Starting at 30 with a 50% savings rate typically leads to financial independence by the mid-to-late 40s.
Is the 4% rule still valid in 2026?
For 30-year retirements, historical data supports it strongly. For 40–60 year early retirements, a 3.25%–3.5% withdrawal rate may offer better long-term safety. Flexibility is the key variable — retirees who reduce spending 10–15% during downturns dramatically improve portfolio survival rates.
Should I include my home equity in my FIRE number?
Typically, no — unless you plan to sell and downsize. Your FIRE number represents investable assets that generate cash flow. A paid-off home reduces monthly expenses (which lowers your FIRE number), but the equity itself doesn’t produce income unless liquidated.
What’s the difference between Lean FIRE and Fat FIRE?
Lean FIRE targets under $40,000 in annual spending with a minimal lifestyle. Fat FIRE targets $100,000+ for a comfortable retirement including travel and discretionary spending. The formula is identical (expenses × 25), but the required portfolio differs dramatically — roughly $1M vs $2.5M+.
How do I adjust my FIRE number for Social Security?
Subtract expected annual benefits from your expenses. If you spend $60,000/year and expect $20,000 from Social Security, the gap is $40,000. FIRE number = $40,000 × 25 = $1,000,000. Some planners use conservative estimates (75–80% of projected benefits) to account for potential reductions.
This article is for informational purposes only and does not constitute investment advice. FIRE calculations are based on historical data and assumptions that may not reflect future market conditions. Always do your own research or consult a licensed financial advisor before making investment decisions.