The 4% Rule: Your Guide to Safe Withdrawal Rates
Understand the famous 4% rule from the Trinity Study — how it works, its limitations, and how to apply it to your FIRE plan.
What Is the 4% Rule?
The 4% rule is the most famous concept in the FIRE community. It states that you can safely withdraw 4% of your portfolio in the first year of retirement, then adjust that amount for inflation each subsequent year, and have a high probability of not running out of money over a 30-year period.
The Trinity Study
The 4% rule comes from the Trinity Study (1998), conducted by three professors at Trinity University. They analyzed historical stock and bond returns from 1926 to 1995 to determine "safe withdrawal rates" for retirees.
Key findings:
- A 4% withdrawal rate had a 95% success rate over 30-year periods
- Success was higher with a portfolio of 50-75% stocks
- Lower withdrawal rates (3-4%) were significantly safer than higher ones (5-7%)
How to Calculate Your FIRE Number
The math is straightforward:
FIRE Number = Annual Expenses ÷ Withdrawal Rate
Using the 4% rule:
FIRE Number = Annual Expenses ÷ 0.04
FIRE Number = Annual Expenses × 25
Examples
| Annual Expenses | Withdrawal Rate | FIRE Number |
|---|---|---|
| $30,000 | 4% | $750,000 |
| $50,000 | 4% | $1,250,000 |
| $80,000 | 4% | $2,000,000 |
| $100,000 | 4% | $2,500,000 |
Is 4% Still Safe?
The debate continues in the FIRE community:
Arguments For 4%
- The Trinity Study used worst-case historical scenarios
- A flexible withdrawal strategy (spending less in down years) significantly improves success rates
- Social Security, part-time work, or other income sources provide a safety buffer
Arguments For a Lower Rate
- Some experts suggest 3.5% or even 3% for very early retirees (50+ year time horizons)
- Current high market valuations (CAPE ratio) may suggest lower future returns
- Healthcare costs and inflation uncertainty add risk
Practical Withdrawal Strategies
Fixed Percentage
Withdraw the same inflation-adjusted amount each year. Simple but rigid.
Variable Percentage Withdrawal
Adjust withdrawals based on portfolio performance. More flexible, better success rates.
Guardrails Approach
Set upper and lower spending limits. Increase spending when the market is up, cut back when it's down.
Our Recommendation
For early retirees (40+ year horizon), we recommend:
- Target a 3.5% initial withdrawal rate for extra safety
- Use a variable withdrawal strategy with spending flexibility
- Maintain a 75% stock / 25% bond portfolio during retirement
- Re-evaluate annually
Use our 4% Rule Calculator to model your personal FIRE scenario.