- What is the 4% Rule and where did it come from?
- The 4% Rule is the rule of thumb that says a retiree can withdraw 4% of their starting portfolio in year one, then adjust the same dollar amount upward for inflation each year afterward, and have a very high chance of the money lasting 30 years. It came from two pieces of research: William Bengen's 1994 paper in the Journal of Financial Planning, and the Trinity Study (Cooley, Hubbard, Walz) published in 1998 and updated in 2011. Both used historical US stock and bond returns going back to 1926 and asked: starting from each year in the dataset, how often would a given withdrawal rate have survived the next 30 years? At 4% with a stock-heavy portfolio, the answer was always — every single rolling 30-year window held up.
- How is annual income calculated?
- Annual income = Portfolio × Withdrawal rate. For a $1,000,000 portfolio at a 4% withdrawal rate, that's $40,000 in year one. The Trinity Study convention is that you take this dollar amount in year one and adjust it upward by inflation each subsequent year, so the real (inflation-adjusted) income stays constant. Monthly income is just annual divided by 12 — for the $1M-at-4% case, $3,333.33 per month, in today's dollars.
- What's a 'real' return and why does it matter?
- Real return = nominal return minus inflation. If your portfolio earns 7% per year nominally and inflation is 3%, your real return is 4%. Real returns are what matter for retirement planning because they measure how much your purchasing power grew, not just the headline percentage. The calculator's projection grows the portfolio at the real return so we can subtract a constant inflation-adjusted withdrawal each year — mathematically identical to working in nominal dollars with a growing withdrawal, but simpler arithmetic.
- Is the 4% Rule still safe in 2026?
- Debated. The Trinity Study used 1926–2009 US data — a period that includes the Great Depression, World War II, the stagflation of the 1970s, and several bear markets. It also covers a period where US equities outperformed almost every other market. Critics like Wade Pfau argue today's bond yields and elevated equity valuations make 4% riskier; their work suggests 3.0–3.5% may be safer for new retirees. Defenders point out that 4% survived 1929, 1966, and 2000 — about as bad as starting conditions get. The honest answer: 4% is a reasonable starting point, but a 30-year retirement plan with no margin for error is fragile. Most planners now recommend 3.5–4% with flexibility to cut spending in bear markets.
- What is sequence-of-returns risk and does this calculator model it?
- Sequence-of-returns risk is the danger that losses early in retirement do more damage than losses later — because the early losses compound against a portfolio you're also drawing down. A retiree who hits 2008 in year 1 ends up far worse than one who hits 2008 in year 20, even if their 30-year average returns are identical. The deterministic projection in this calculator does NOT model sequence risk — it assumes constant returns every year. The Trinity Study reference table does, because it tested every actual historical starting year. That's why a 4% rate shows 96% success even with strong long-run averages: the 4% that failed were specifically the windows starting just before a major crash.
- Why does the deterministic projection sometimes say 'survives' when Trinity says it failed?
- Because they're answering different questions. The deterministic projection asks: if my real return is exactly X% every year, will the portfolio last? Trinity asks: across every historical rolling window of bumpy real returns, how often did the portfolio last? Constant returns are kinder to portfolios than the same average return delivered with volatility — you never get hit by an early crash. If your projection says 'survives 30 years' but Trinity shows a meaningful failure rate at your withdrawal rate, take the lower number as the more honest estimate.
- How do taxes and fees affect this?
- The calculator does not subtract taxes or fees — both come out of your withdrawal in the real world. If you pull $40,000 from a traditional IRA, the IRS treats it as ordinary income; depending on your bracket, you may net $30,000–$35,000. Investment fees (expense ratios, advisor fees) reduce your real return — every 0.5% in fees roughly translates to a 0.5% lower real return assumption. The Trinity Study used gross returns, so its success rates implicitly assume no fees and no taxes. To be realistic, lower your expected return by your fee drag and remember that your withdrawal needs to cover the tax bill.
- What about a 40 or 50-year retirement for early retirees?
- Longer horizons push the safe withdrawal rate down. The Trinity 4% number is for 30 years; for 50 years, most research suggests something closer to 3.0–3.5%. The intuition is straightforward: at 4%, the portfolio is consumed at a rate slightly faster than typical real returns can replenish — over 30 years that's fine for most sequences; over 50 years the math gets meaner. FIRE planners typically use the 3.5% rule for this reason. The calculator lets you change the horizon and recompute — try 40 or 50 with a 3.5% rate and see how the projection holds.
- Does this account for Social Security or a pension?
- No. The calculator treats your portfolio as the only income source. If you'll have Social Security, a pension, or rental income, subtract that from your spending needs before computing how much you need the portfolio to provide. Example: you need $60,000/year and Social Security covers $20,000; you only need $40,000 from the portfolio, which at 4% means a $1M portfolio target — not $1.5M. Conservative planners discount Social Security by 25–30% for younger workers to account for possible benefit cuts; that's a personal call.
- Can I withdraw at a higher rate if my portfolio is doing well?
- Yes — and most retirees do something like this in practice. The constant-real-dollar withdrawal of the Trinity Study is a worst-case rule, not a recipe. Variable withdrawal strategies (Guyton-Klinger, the Bogleheads' VPW, percentage-of-portfolio rules) explicitly raise withdrawals after good years and cut them after bad ones. They produce higher average lifetime spending than the 4% Rule but require you to actually cut spending in down years — a behavioral test as much as a financial one. The 4% Rule's appeal is that it's a single number you can commit to in advance, including the parts where the market falls 40% and you keep withdrawing the same amount.
