Trinity Study Retirement Success Calculator
Historical 30-year portfolio success rate for any withdrawal rate + stock/bond allocation, from the canonical Trinity Study (Cooley/Hubbard/Walz 1998). Free.
Trinity Study Portfolio Success Calculator
The Trinity Study asked a precise question: across every historical 30-year retirement since 1926, how often did an inflation-adjusted withdrawal survive the full period? Enter a withdrawal rate and a stock/bond allocation to see the historical success rate — and how much the allocation changes the odds.
Success rate by allocation (at 4.0%)
How to Use the Trinity Study Calculator
Pick your withdrawal rate
The percentage of your starting portfolio you'd withdraw in year one, then increase by inflation each year after. 4% is the classic Trinity/Bengen figure; FIRE retirees with 40+ year horizons often use 3–3.5%.
Set your stock allocation
The share of the portfolio in stocks (the rest in bonds). This is the variable the Trinity Study made famous: too few stocks and inflation erodes the portfolio; too many and volatility threatens it. The historical sweet spot sits around 50–75% stocks.
Read the headline success rate
The share of historical 30-year periods in which that rate + allocation never ran the portfolio dry. 95%+ is robust; below 90% means you're relying on an above-average sequence of returns.
Compare across allocations
The grid shows the same withdrawal rate at all five allocations. Use it to see how much moving from, say, 25% to 75% stocks improves your odds — usually far more than people expect at higher withdrawal rates.
The Trinity Study — Where the 4% Rule Got Its Confidence Interval
What the Three Professors Actually Did
In 1998, three finance professors at Trinity University in San Antonio — Philip Cooley, Carl Hubbard, and Daniel Walz — published "Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable" in the AAII Journal. William Bengen's 1994 paper had already proposed the 4% rule, but the Trinity Study reframed the question in the language retirees actually care about: not "what is the single safe rate?" but "for a given withdrawal rate and stock/bond mix, what percentage of historical periods succeeded?" They backtested every overlapping retirement window from 1926 to 1995 — 41 of them at 30 years — using US large-cap stock returns and long-term high-grade corporate bond returns, across five allocations (100/0, 75/25, 50/50, 25/75, 0/100) and a range of withdrawal rates, for horizons of 15, 20, 25, and 30 years. The output was a now-famous grid of success percentages.
The headline finding (Table 3 of the paper): an inflation-adjusted 4% withdrawal from a portfolio with at least 50% stocks succeeded in 95–98% of the 41 historical 30-year periods — 95% at 100% stocks, 98% at 75/25, 95% at 50/50. Push the rate to 5% and success falls — to 76% at 50/50 and 83% at 75/25. Drop to 3% and every period survived at any allocation that held stocks; even 100% bonds survived 80% of periods. The study made two things undeniable: withdrawal rate dominates the outcome, and a meaningful stock allocation is not optional — a 100% bond portfolio succeeded in only 20% of 30-year periods at 4%, because fixed-income returns couldn't outrun inflation over 30 years. The same three authors updated the work in the Journal of Financial Planning (April 2011) with data through December 2009 — 55 overlapping 30-year periods — and reported, for example, 82% success for a 5% inflation-adjusted withdrawal from 75/25 and 45% at 7%. This calculator uses the 1998 table the study is known for; the update moves individual cells by a few points without changing the shape.
"The Trinity Study's quiet revolution was the word 'probability'. It turned 'how much can I spend?' from a single risky number into a distribution — and showed that the bond-heavy 'safe' portfolio was often the riskiest of all over a 30-year retirement."
How to Read a Success Rate — and Its Limits
A 95% historical success rate does not mean a 95% chance your retirement will work; it means that in the 1926–1995 US data, 95% of the 41 thirty-year windows survived. That sample is the 20th-century US equity market, which Wade Pfau's 2010 study of 17 developed markets showed sat near the favourable end of the international range. It also excludes the future: high equity valuations and the possibility of a long low-return stretch are reasons some later researchers argue for 3–3.5% over very long horizons. The Trinity tables are also strictly 30-year — a 45-year-old retiring early faces a 50-year horizon the study never tested, where safe rates fall further. Treat the success rate as a well-anchored historical baseline, not a guarantee, and pair it with a cash buffer and willingness to trim spending after a bad year.
For retirees in Singapore, Malaysia, and the wider ASEAN region, the Trinity framework still travels, but the inputs need translating. CPF (Singapore) and EPF (Malaysia) already provide a partly annuitised, lower-volatility income floor — so the portfolio the 4%/Trinity math applies to is only the supplementary investment pot on top of those schemes, which sharply reduces the required portfolio. A globally diversified portfolio anchored in US and developed-market equities can reasonably borrow the 3.5–4% range; a portfolio concentrated in a single smaller home market historically supported a lower safe rate. Currency matters too: if you earn in SGD or MYR but hold USD assets, exchange-rate swings add a layer of sequence risk the original US-only study never modelled. The sensible adaptation is to lean toward the conservative end of the grid and let CPF/EPF carry the non-negotiable spending.
An all-bond portfolio failed more than half the time
The Trinity Study (1998) was authored by Cooley, Hubbard & Walz of Trinity University, Texas — hence the name.
It reframed Bengen's 4% rule as a grid of success probabilities across withdrawal rates and stock/bond mixes.
An inflation-adjusted 4% withdrawal survived ~95% of historical 30-year periods at 50%+ stocks.
At 5%, success fell to 76% (50/50) and 83% (75/25) — a one-point rate change, a large change in the odds.
A 100% bond portfolio survived only 20% of 30-year periods at 4% — inflation outran fixed income over 30 years.
The study used US data 1926–1995 — 41 overlapping 30-year windows of S&P 500 and long-term high-grade corporate bond returns.
The historical sweet spot was 50–75% stocks — enough growth to beat inflation, enough bonds to dampen crashes.
Original horizons were 15, 20, 25 and 30 years; this tool uses the canonical 30-year table.
Wade Pfau's 2010 study of 17 developed markets found the US near the favourable end — most others supported lower safe rates.
For 40+ year (FIRE) horizons — which the study never tested — later research argues for 3–3.5%, below the classic 4%.
Frequently Asked Questions
- A 1998 paper by three Trinity University professors (Cooley, Hubbard, Walz) that tested retirement withdrawal rates against historical US market data from 1926 to 1995. For each combination of withdrawal rate and stock/bond allocation, it reported the percentage of historical 30-year periods in which an inflation-adjusted withdrawal never exhausted the portfolio. It's the study that gave the 4% rule its famous "~95% success" confidence figure.
- Bengen's 4% rule (1994) answered "what is the maximum safe rate?" with a single number. The Trinity Study answered "for a given rate AND allocation, what fraction of history succeeded?" — turning one number into a probability grid. Our companion safe-withdrawal-rate-calculator applies the 4% rule to turn a portfolio into a spend; this tool shows the historical odds behind a chosen rate and allocation.
- No. It means 95% of the 41 historical 30-year windows in the 1926–1995 US data survived. The future may differ — high stock valuations and the chance of a long low-return stretch are reasons some researchers now use 3–3.5% for long horizons. The US sample was also near the favourable end of Pfau's 17-country comparison. Read the success rate as a strong historical baseline, not a forward-looking guarantee.
- Over a 30-year retirement, inflation is the silent killer. A bond-heavy portfolio feels "safe" because it doesn't swing much, but its returns historically couldn't outrun decades of inflation while you withdrew from it — a 100% bond portfolio survived only 20% of 30-year periods at 4%. Stocks provide the growth that keeps the portfolio ahead of inflation. The Trinity grid shows the historical sweet spot was 50–75% stocks: enough growth, with bonds to soften crashes.
- The canonical 30-year table — the horizon the Trinity Study is best known for and the standard for a traditional retirement starting in your 60s. Shorter horizons (15–25 years) had higher success rates; longer horizons (40–50 years, common for early retirees) had lower ones. If you're retiring early, treat the 30-year figures as optimistic and lean toward a lower withdrawal rate, or use our safe-withdrawal-rate-calculator which discusses 3.0–3.5% for 40+ year horizons.
- No — the success rate applies only to portfolio withdrawals. Guaranteed income streams (US Social Security, a pension, Singapore CPF LIFE, Malaysia EPF) are separate and reduce the spending your portfolio must cover. The right approach: subtract those income streams from your target spending, then apply the withdrawal rate only to the remaining gap. This often shrinks the required portfolio dramatically.
- Yes. The figures here are for the inflation-adjusted method: withdraw the chosen percentage of the starting portfolio in year one, then increase that dollar amount by inflation every subsequent year, regardless of market performance. The Trinity Study also reported a "non-inflation-adjusted" set with higher success rates, but the inflation-adjusted version is the realistic one — your spending needs rise with prices.
- Four levers: (1) lower the withdrawal rate — even 0.5% makes a large difference; (2) move toward the 50–75% stock sweet spot if you're too bond-heavy; (3) build a 2–3 year cash buffer so you don't sell stocks during a crash (mitigates sequence-of-returns risk); (4) plan to trim spending 10% after a bad market year (the Guyton-Klinger guardrails). Part-time income in the first decade of retirement is also one of the most powerful fixes.
- The framework travels; the numbers don't transfer directly. The study used 20th-century US returns, which were exceptionally strong. Wade Pfau's 2010 study of 17 developed markets found most supported lower safe rates than the US. For ASEAN investors, a globally diversified portfolio anchored in developed-market equities can borrow the 3.5–4% range, but a portfolio concentrated in one smaller home market historically supported less. Add currency risk if you spend in SGD/MYR but invest in USD assets, and let CPF/EPF cover your essential spending.
- No. The Trinity Study uses historical "sequence" backtesting — it replays actual overlapping 30-year windows of real returns. Monte Carlo instead generates thousands of random return paths from an assumed distribution. Both have merits: historical backtesting captures real correlations and crashes that occurred together; Monte Carlo explores paths history hasn't produced yet. Many planners look at both. This calculator reports the historical (Trinity) result.
Method & sources
How it computes
Looks up the Trinity Study's Table 3 — the percentage of the 41 overlapping 30-year periods from 1926 to 1995 in which an inflation-adjusted withdrawal at the chosen initial rate never exhausted a rebalanced portfolio of S&P 500 stocks and long-term high-grade corporate bonds — for the five published allocations (100/0, 75/25, 50/50, 25/75, 0/100) at 3–12% withdrawal rates, and linearly interpolates between the published rates and allocations. First-year withdrawal = portfolio × rate.
What this tool implements
- Cooley, Hubbard & Walz (1998) Table 3: inflation-adjusted (CPI) withdrawals, 30-year payout period, 1926–1995, annual rebalancing; success = portfolio value ≥ 0 at the end of the period
- Published columns 3%–12% and rows 100/75/50/25/0% stocks are used as given; values between them are linear interpolations, and rates below 3% are extrapolated and clamped to 100
- The 30-year table only; the study's 15-, 20- and 25-year tables and its nominal-withdrawal table are not used
- The authors' 2011 update (Journal of Financial Planning, data to December 2009, 55 overlapping 30-year periods) is described on the page but not used
Sources
- Cooley PL, Hubbard CM, Walz DT. Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable. AAII Journal 1998;20(2):16-21. https://www.aaii.com/files/pdf/6794_retirement-savings-choosing-a…
- Cooley PL, Hubbard CM, Walz DT. Portfolio Success Rates: Where to Draw the Line. Journal of Financial Planning, April 2011. https://www.financialplanningassociation.org/article/journal/APR1…
- Bengen WP. Determining Withdrawal Rates Using Historical Data. Journal of Financial Planning 1994;7(4):171-180.
- Pfau WD. An International Perspective on Safe Withdrawal Rates from Retirement Savings: The Demise of the 4 Percent Rule? Journal of Financial Planning 2010;23(12):52-61.
What can make this go out of date
- none at runtime — the table is a fixed historical result
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