4% Rule Calculator

How to use this calculator

Enter your annual retirement expenses and the calculator computes your required portfolio using the 4% rule. Optionally enter your current savings, monthly contribution, and expected return to see how many years until you reach your FIRE number.

Annual Retirement Expenses should be your actual budget in today’s dollars. Pull 12 months of bank and credit card statements. Most people underestimate by 15% to 25% when working from memory.

The calculator also shows the 25x multiplier behind the 4% rule and compares your target across different withdrawal rates: 3%, 3.5%, 4%, and 4.5%.

Where the rule came from

William Bengen was a financial planner in California when he published a paper in the Journal of Financial Planning in October 1994. He was trying to answer a concrete client question: how much can you withdraw each year without running out of money?

Before his paper, retirement planning used rough rules of thumb. Planners often suggested 5% or 6%, based on projected returns rather than actual historical sequences. Bengen ran the first systematic backtests, asking what would have happened to retirees starting in 1926, 1927, 1928, and every subsequent year through 1992.

The answer was stark. Withdrawal rates above 4% failed in multiple historical periods. At 4%, every 30-year sequence survived. The worst period was starting in 1966, right before the 1970s stagflation: high inflation, low real equity returns, and a brutal early sequence.

The formula

One critical point: the 4% rule does not mean you withdraw 4% of your current balance every year. You withdraw the Year 1 dollar amount, then increase it by inflation each year. If your portfolio grows to $2M, you still withdraw roughly $60,000 adjusted for inflation, not $80,000. Recalculating 4% of the current balance annually is a different (and more aggressive) strategy.

What the Trinity Study added

Four years after Bengen’s paper, three finance professors at Trinity University published what became known as the Trinity Study. They tested withdrawal rates across multiple time horizons and portfolio allocations.

Their key findings for a 30-year retirement:

The stock-heavy portfolios outperform at higher withdrawal rates because long-term equity returns outpace inflation more reliably than bonds. A retiree who holds mostly bonds for perceived safety actually faces a higher failure rate at 4% than one holding mostly stocks. The intuition that bonds are “safer” for retirees is partially wrong. Lower volatility in the short run doesn’t translate to better portfolio survival over 30-year periods.

The multiplier table

The 4% rule uses a 25x multiplier (1 ÷ 0.04 = 25). Different withdrawal rates have their own multipliers:

A 35-year-old planning a 50-year retirement should use 28.6x or 33.3x rather than 25x. The 4% rule was validated for 30-year horizons. Using it for a 50-year retirement means accepting a higher failure rate than the original research implies.

The choice of multiplier matters in real dollar terms. For someone targeting $70,000 per year:

• At 25x: need $1,750,000
• At 28.6x: need $2,002,000
• At 33.3x: need $2,331,000

The difference between 25x and 33.3x is $581,000. For many people, that’s several additional years of work. Choosing the right multiplier for your actual situation is worth getting right.

Legitimate criticisms of the rule

US exceptionalism. The rule uses US market data. The US was the dominant global economy for most of the 20th century and had exceptional equity returns. Wade Pfau analyzed actual market data from 17 countries and found a globally applicable safe withdrawal rate closer to 3% to 3.5%. If your portfolio is globally diversified or you live outside the US, the historical US numbers are optimistic.

Starting valuation matters. Michael Kitces found that 10-year returns correlate strongly with starting market valuations. When the cyclically adjusted P/E ratio (CAPE) is above 20 to 25, expected returns over the next decade are lower. Retiring during a high-valuation environment historically reduces the safe withdrawal rate for that cohort.

Bond yields at the time. The original research included periods when 10-year Treasury bonds yielded 5% to 10%. In low-yield environments, bonds contribute far less to portfolio returns, reducing the durability of balanced portfolios.

Medical inflation. The rule assumes expenses grow at general CPI. Medical costs have historically inflated at 5% to 8% annually. A plan that works at 4% might underestimate true spending growth for retirees with significant healthcare costs.

Despite all of this, the 4% rule remains a reasonable planning heuristic. The criticisms mostly argue for 3% to 3.5%, not for abandoning the framework.

Social Security changes the calculation

The 4% rule assumes all retirement income comes from your portfolio. For most Americans, that’s not accurate.

Social Security benefits average about $22,000 per year for a retired individual. A couple with both spouses having worked full careers can collect $40,000 to $80,000 per year combined.

If Social Security covers $40,000 of your $80,000 annual expenses, your portfolio only needs to cover $40,000. Your FIRE number drops from $2,000,000 to $1,000,000.

Early retirees who stop working at 40 or 45 may have significantly reduced Social Security benefits due to fewer years of earnings history. But someone who works until 55 or 60 with a substantial earnings record has a meaningful Social Security floor, even claiming early at 62.

Waiting to claim Social Security from 62 to 70 increases benefits by about 76%, roughly 8% per year from full retirement age. For anyone in reasonable health, waiting to 70 is almost always the mathematically correct decision. The break-even point is age 79 to 80: anyone who lives past that collects more total benefits by waiting.

Practical strategies to make the rule more durable

Flexible spending. Willingness to reduce spending 10% to 20% in bad market years dramatically improves portfolio survival in simulations. You don’t need to commit to permanent cuts, just the ability to have a leaner year when markets are down 30%. This converts a static withdrawal problem into a dynamic one, which historical data shows is significantly more resilient.

Part-time income in early retirement. Even $10,000 to $15,000 per year from occasional consulting or freelancing eliminates portfolio withdrawals in bad years. This removes the most dangerous scenario (forced selling at the bottom) almost entirely. A retiree who earns $15,000 part-time and spends $60,000 only needs to withdraw $45,000 from the portfolio in that year.

Bond tent. Start retirement with a higher bond allocation (40% to 50%) and gradually shift to more equities over the first 10 years. The early bond cushion absorbs sequence risk. Then equity exposure increases just as the high-risk early period ends. Kitces and Pfau research shows this counterintuitive approach improves success rates compared to a static allocation.

Delay Social Security. Every year you wait from full retirement age to age 70 adds 8% to your monthly benefit permanently. For married couples, the higher-earning spouse should almost always delay to 70 to maximize the survivor benefit.

Running multiple strategies simultaneously (flexible spending, part-time income, delayed Social Security) moves the effective failure rate extremely close to zero in historical data, even at a 4% initial withdrawal rate.

The 4% rule and early retirement specifically

The 4% rule is commonly cited in FIRE communities, but it was designed for conventional retirement (roughly age 60 to 65) with a 30-year horizon. For someone retiring at 35, it’s an incomplete tool.

A 35-year-old who retires today might need income for 55 to 60 years. Historical success rates at 4% over that horizon drop to around 75% to 80%. That’s acceptable if you have spending flexibility, but it’s not the near-certainty that the 4% rule implies for 30-year horizons.

Early FIRE retirees have several factors working in their favor that partially offset this:

Years to adjust. Someone who retires at 35 and discovers by age 42 that markets have been bad has time to return to part-time work, reduce spending, or make other adjustments. A 65-year-old has less runway.

Social Security waiting period. An early retiree who doesn’t claim Social Security until 70 is bridging a finite period (retirement to 70) with a higher withdrawal rate, then transitioning to a lower withdrawal rate when Social Security kicks in. This reduces long-run portfolio depletion risk significantly.

Human capital flexibility. Skills don’t expire. A 40-year-old who spent 15 years as an engineer, doctor, or consultant can return to work at meaningful income levels if needed. This implicit flexibility functions as insurance that doesn’t appear in the withdrawal rate calculation.

For early retirees specifically, treat 4% as a ceiling, not a target. The right number depends on your specific horizon, flexibility, and supplemental income sources.

Practical examples at different spending levels

The 4% rule produces very different financial realities depending on where you set your spending target. Here’s a comparison across common spending levels:

Each step up in annual spending roughly doubles the required accumulation at the extremes. A $150,000 annual budget requires 5x the portfolio of a $30,000 budget.

The insight this table produces: most people who feel they “need” $100,000 per year in retirement have never actually modeled what $70,000 or $80,000 buys in a paid-off home with no commuting costs, no work wardrobe, no work lunches, and time to cook rather than ordering out. Retirement spending is structurally different from working-life spending.

Running the numbers at two or three spending levels before committing to a target is worth doing. A $15,000 reduction in annual spending reduces the FIRE number by $375,000 and potentially the timeline by 3 to 5 years.