Trinity Study & Safe Withdrawal Rate (SWR) Simulator

4% Rule Simulator

Work out the capital you need to retire and check with real historical data (1928-2025) how often a withdrawal rate would have lasted 30 years.

$2,000
4.0%
$10,000
$400
7%

Target Retirement Capital

$600,000
--
--
96%
Your Contributions
Compound Interest
Target Retirement Capital
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How the 4% rule calculator works

The calculator estimates the capital you need to live off your investments and how many years it will take to get there at your current savings rate. Enter your monthly spending, the withdrawal rate, current savings, monthly contribution and expected return.

The target capital is annual spending divided by the withdrawal rate:

Target capital = Monthly spending × 12 ÷ Withdrawal rate

Worked example

With spending of €2,000 a month (€24,000 a year), the target is €600,000 at a 4% rate, €685,714 at 3.5% and €800,000 at 3%. A lower withdrawal rate raises the capital required but reduces the risk of running out of money in long retirements.

Where the success rate comes from

We calculate the “historical success rate” from real data: the share of 30-year periods since 1928 in which a 60/40 portfolio (S&P 500 and 10-year US Treasuries), with inflation-adjusted withdrawals, did not run out. At 4% it is about 94%; at 5% it falls to 72%. To test your own mix, horizon and fees, or see it across 5,000 Monte Carlo scenarios, use the retirement simulator.

Assumptions and limits

  • Horizon. The study covers 30 years. For 40- or 50-year retirements, many planners use 3% to 3.5%.
  • Market and currency. The data are US market returns in dollars. A European investor faces different inflation, currency and taxes.
  • Taxes and fees. The withdrawal rate applies before tax; fees reduce the safety margin.
  • Savings projection. Years to target use a constant average return and contributions at the end of each month.

More detail in our methodology.

Frequently asked questions

Does the 4% rule work for retiring before 50?
Over horizons longer than 30 years the risk of depleting the portfolio rises. For very early retirement, 3% to 3.5% is common, or keeping flexibility to cut spending in bad years.
Is the 4% recalculated each year on the balance?
No. In the Trinity Study you withdraw 4% of the initial capital in the first year and then adjust that amount for inflation every year, regardless of portfolio performance.
Which return should I use for the years to target?
If your target is in today's money, use a return net of fees and inflation, for example 3% to 5% for a diversified portfolio. If you use a nominal return, the target should also grow with inflation.
Is this investment advice?
No. It is an educational tool based on historical data. Past returns do not guarantee future returns.