CalculateY
Quick Answer
A household spending an estimated $50,000/year with a 4% safe withdrawal rate needs approximately $1,250,000 to reach FIRE. Starting with $100,000 and contributing $30,000/year at 7% returns, the estimated time to FIRE is approximately 16 years.
Common Examples
| Input | Result |
|---|---|
| Expenses $50,000/yr, 4% SWR, $100K saved, $30K/yr contribution, 7% return | Estimated FIRE number: $1,250,000, approximately 16 years |
| Expenses $40,000/yr, 4% SWR, $0 saved, $30K/yr contribution, 7% return | Estimated FIRE number: $1,000,000, approximately 19 years |
| Expenses $60,000/yr, 3.5% SWR, $200K saved, $40K/yr, 7% return | Estimated FIRE number: $1,714,286, approximately 17 years |
| Expenses $30,000/yr, 4% SWR, $500K saved, $20K/yr, 7% return | Estimated FIRE number: $750,000, approximately 4 years |
How It Works
The FIRE number formula
The core formula is straightforward:
FIRE Number = Annual Expenses / Safe Withdrawal Rate
At a 4% SWR and $50,000 in annual expenses: $50,000 / 0.04 = $1,250,000. Once a portfolio reaches that level, withdrawing 4% per year covers living expenses indefinitely, based on historical market data.
The 4% rule origin
The 4% rule comes from the Trinity Study, published in 1998 by three finance professors at Trinity University. They analyzed historical U.S. stock and bond returns from 1925 to 1995 and found that a 4% annual withdrawal from a balanced portfolio succeeded across 30-year retirement periods in most historical scenarios. It is not a guarantee; it is a historically derived planning benchmark.
Safe withdrawal rate considerations
A 4% SWR suits a roughly 30-year retirement horizon. For longer horizons, such as those common in early retirement, many practitioners use 3% to 3.5% to reduce sequence-of-returns risk. A 3% SWR on $50,000 in annual expenses produces a FIRE number of approximately $1,666,667. The more conservative the rate, the larger the required portfolio.
Monthly compounding projection
To estimate years to FIRE, this calculator runs an iterative monthly simulation:
For each month: Balance = Previous Balance x (1 + r/12) + Monthly Contribution
Where r is the annual return rate as a decimal. The simulation runs until the balance meets or exceeds the FIRE number, or until 100 years have elapsed. If inflation is included, the FIRE target grows each month to account for rising expenses.
Savings rate vs. return rate
The savings rate (annual contribution relative to income) has a larger short-term effect on FIRE timeline than investment returns, particularly in the early accumulation years when the portfolio is small. A household that saves $40,000 per year reaches the $1,000,000 FIRE number faster than one earning 1% more in returns but saving $25,000 per year. Both matter, but the savings lever is more directly controllable.
Worked example
Annual expenses: $50,000. SWR: 4%. FIRE number: $50,000 / 0.04 = $1,250,000.
Starting balance: $100,000. Annual contribution: $30,000 ($2,500/month). Annual return: 7%. Monthly return: 0.07 / 12 = 0.005833.
Month 1: $100,000 x 1.005833 + $2,500 = $103,083. Month 2: $103,083 x 1.005833 + $2,500 = $106,184. This continues month by month. After approximately 192 months (16 years), the balance reaches an estimated $1,250,000. Total contributions over that period: approximately $580,000. Estimated investment growth: approximately $670,000.
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