4% Rule Calculator — Find Your Safe Retirement Withdrawal Amount

The 4% rule calculator answers the central question of retirement planning: how much can you safely withdraw from your portfolio each year without running out of money? Based on the influential Trinity Study, the 4% rule suggests that withdrawing 4% of a portfolio in the first year of retirement, then adjusting that dollar amount for inflation each subsequent year, has historically sustained a 30-year retirement with a high success rate using a diversified stock and bond portfolio. This calculator works in both directions: given your portfolio size, it shows your safe annual withdrawal amount, and given your annual expenses, it shows exactly how large a portfolio you need to retire.

How to use this 4% Rule Calculator

1. 1Enter your current portfolio value — the total in retirement and investment accounts you plan to draw from.
2. 2Optionally enter your annual retirement expenses to check whether your current portfolio is large enough to support them.
3. 3Select a safe withdrawal rate. 4% is the traditional benchmark, though many planners now recommend 3-3.5% for longer retirements or more conservative planning.
4. 4Read your maximum safe annual and monthly withdrawal amount, the portfolio size required to cover your expenses, and whether your current portfolio meets that target.

4% rule (safe withdrawal rate) formula explained

The 4% rule has two equivalent forms depending on which number you are solving for. If you know your portfolio size, multiplying by the withdrawal rate gives your safe annual spending amount. If you know your target annual expenses, dividing by the withdrawal rate gives the portfolio size needed — this is sometimes called the "25x rule" at a 4% rate, since dividing by 0.04 is the same as multiplying by 25.

4% rule example: $1,000,000 portfolio, $50,000 annual expenses

1. 01Portfolio: $1,000,000. Withdrawal rate: 4%.
2. 02Max safe annual withdrawal: $1,000,000 × 0.04 = $40,000.
3. 03Required portfolio for $50,000/year expenses: $50,000 ÷ 0.04 = $1,250,000.
4. 04Current portfolio ($1,000,000) is below the required amount ($1,250,000) by $250,000.

What affects whether the 4% rule will work for your retirement?

Tips and things to know

• ✓Treat the 4% rule as a starting estimate, not a guarantee — it is based on historical US market data and does not account for unusually poor sequences of early returns, which can meaningfully affect long-term portfolio survival.
• ✓If your retirement horizon is longer than 30 years (common for early retirees), consider testing a 3-3.5% withdrawal rate instead, which historically has a higher success rate over longer periods.
• ✓The "25x annual expenses" shortcut (dividing expenses by 0.04) is a quick mental math version of the same calculation this calculator performs — useful for quick estimates without pulling up a calculator.
• ✓Consider a flexible withdrawal strategy that reduces spending slightly during market downturns, rather than a rigid fixed withdrawal — research suggests this can improve portfolio survival rates compared to the strict version of the rule.
• ✓Recalculate periodically as your portfolio value and expenses change — the 4% rule is most useful as an ongoing planning check, not a single calculation done once at retirement.

4% Rule Calculator — bottom line

The 4% rule is one of the most cited retirement planning guidelines — and one of the most misunderstood. It originated from the Trinity Study (1994, updated multiple times), which found that a 4% initial withdrawal rate from a balanced stock-bond portfolio survived 30-year retirement windows with a 95%+ success rate using 20th-century US market data. Three critical caveats are often omitted: first, it is a 30-year rule, not a forever rule. Early retirees with 40–50-year horizons face meaningfully higher sequence-of-returns risk, and a 3–3.5% rate is more conservative and appropriate. Second, the rule assumes you withdraw the same inflation-adjusted dollar amount every year regardless of portfolio performance — which is not how most retirees actually behave or should behave. Third: the original study used a 50/50 stock/bond allocation. The most common mistake is treating the 25× portfolio number as an on/off switch. Retirees who reach exactly their FIRE number and immediately begin 4% withdrawals have zero buffer for a market downturn in their first year. A 20% market decline in year one of retirement reduces the portfolio and the sustainable withdrawal rate simultaneously — this sequence-of-returns risk is the biggest threat to early retirement. A practical buffer: aim for 28–30× annual expenses rather than 25×, giving you a 10–20% margin. Stress-test your number against a 3.5% withdrawal rate in this calculator and confirm it still covers your expenses. That is your real safety margin.

Official resources and further reading