Retirement Corpus Needed Calculator
Retirement corpus is the lump sum of investments needed at retirement to fund withdrawals for life. The standard answer: 25 times your annual desired retirement spending.
Retirement Corpus Calculator
Working calculator with inflation-aware corpus targeting and contribution shortfall analysis.
Open Retirement Corpus Calculator →About this tool
Retirement corpus is the invested-portfolio target you need to hit by your retirement date so that inflation-adjusted withdrawals can fund your spending for life without depleting the portfolio. The default formula is 25 times annual retirement spending, derived directly from the 4 percent safe withdrawal rate (SWR) that William Bengen documented in 1994 and that the Trinity Study (Cooley, Hubbard, Walz 1998) replicated using US stock and bond returns from 1925 to 1995.
The 25x multiplier is a shorthand for a much messier underlying calculation: the SWR is the highest first-year withdrawal percentage that historically survived 30 years across all possible retirement start dates, with annual inflation adjustments and a 50/50 to 75/25 stock-bond allocation. Modern research extends this for early retirement (50+ year horizons), international portfolios, and current valuation levels, all of which can move the multiplier from 25x up to 33x.
How it works
Corpus needed = Annual desired spending / Safe Withdrawal Rate At 4% SWR = Annual spending x 25 At 3.5% SWR = Annual spending x 28.6 (typical for 40-year retirement) At 3% SWR = Annual spending x 33.3 (typical for 50+ year retirement) With SS offset = (Annual spending - Expected SS) x Multiplier
- Annual desired spending = full retirement budget in today's dollars (housing, food, healthcare, travel, gifts, taxes).
- Safe Withdrawal Rate = 4 percent for 30-year retirements, 3.5 percent for 40-year, 3.0 to 3.25 percent for 50+ year early-retirement horizons.
- Expected SS = projected Social Security benefit at full retirement age, optional to net out.
- Multiplier = 1 / SWR. The inverse of the withdrawal rate.
Worked example
Consider a US household planning to retire at 65 in 2026 with $80,000 desired annual spending and a projected joint Social Security benefit of $36,000 per year starting at 67:
- Net spending need: $80,000 - $36,000 = $44,000 per year that the portfolio must cover post-67.
- Bridge years 65-67: portfolio must also cover the full $80,000 for 2 years = $160,000 in bridge cash/bonds.
- Core corpus at 4 percent SWR (30-year): $44,000 x 25 = $1,100,000.
- Add bridge: $1,100,000 + $160,000 = $1,260,000 total corpus.
- Healthcare buffer (Fidelity 2025): add $250,000 for a couple's out-of-pocket healthcare over retirement, giving $1,510,000.
- Early-retirement variant at age 55: bump SWR down to 3.25 percent. Without SS for 12 bridge years, corpus = $80,000 / 0.0325 = $2,461,000.
Corpus multipliers by retirement horizon
| Horizon | Safe withdrawal rate | Multiplier | Confidence |
|---|---|---|---|
| 20 years (age 70 retire) | 5.0% | 20x | Very high (Bengen extended) |
| 30 years (standard 65) | 4.0% | 25x | High (Trinity Study) |
| 35 years | 3.75% | 26.7x | High |
| 40 years | 3.5% | 28.6x | High (Pfau 2024) |
| 45 years | 3.25% | 30.8x | Medium |
| 50+ years (FIRE) | 3.0% to 3.25% | 30 to 33x | Medium (Kitces) |
| Perpetuity (endowment) | 2.5% to 2.75% | 36 to 40x | Endowment-style |
Common mistakes
- Using gross income instead of net spending. Subtract retirement taxes, pre-retirement payroll deductions, and FICA from your current take-home to estimate true retirement spending. Most workers overshoot by 20 to 30 percent.
- Ignoring sequence-of-returns risk. A 30 percent market drop in retirement year one is much more destructive than the same drop in year 20. Hold 1 to 3 years of expenses in cash or short bonds as a sequence buffer.
- Mixing nominal and real numbers. If your target is in today's dollars, your withdrawals and returns must also be in real terms. Mixing nominal returns (7 percent) with real spending leads to massive overestimates of safe withdrawal.
- Double-counting Social Security. Either subtract SS from spending before applying 25x, OR carry it separately as outside income; never both.
- Forgetting healthcare's lumpy timing. Healthcare costs spike before Medicare (age 65) and again in late retirement (long-term care). Build a separate healthcare bucket, not just a flat annual line.
- Treating 25x as a precise number. It is a baseline with roughly 5 percent historical failure rate at 30 years and assumes US-only data and a stock-heavy portfolio. Treat it as the floor for further stress-testing, not the answer.
Related tools and concepts
Frequently asked questions
Is the 4 percent rule still safe in 2026?
For 30-year retirements based on US historical data, yes; the original Trinity Study and Bengen's 1994 paper showed over 95 percent success rate at 4 percent in 60/40 portfolios. For 50-year early-retirement horizons, modern research (Pfau, Kitces, Morningstar 2024) recommends dropping to 3.0 to 3.5 percent. For non-US portfolios with worse historical sequences (Japan, UK, much of Europe), adjust further down to 3.0 percent. Today's higher TIPS real yields (~2 percent) actually support slightly higher SWRs than the deep-low-yield environment of 2020 to 2022.
Does the corpus include Social Security?
Most planners EXCLUDE Social Security from the corpus calculation as a margin of safety. If you DO count it, the corpus needed shrinks dramatically: a maximum 2026 SS benefit of approximately 48,200 USD/year at full retirement age covers 1.2 million USD of 25x corpus need. A middle-income SS benefit of 24,000 USD/year covers 600,000 USD. The cleaner approach: subtract expected SS from desired annual spending, then apply 25x to the residual.
What return rate should I assume?
5 percent real return (after inflation) is conservative and defensible. 7 percent nominal at 3 percent inflation is the historical US stock-only return. A 60/40 stock-bond mix delivers roughly 5 percent real over long horizons. Use 4 percent real for additional margin of safety, 6 percent real if you have a long pre-retirement runway and high equity allocation. Most credible 2025 to 2026 forecasts (Vanguard, BlackRock, Morningstar) project 5 to 6 percent real for 60/40 over the next decade.
How does inflation factor into the corpus calculation?
Two ways. First, choose whether your desired spending is in today's purchasing power (real dollars) or future nominal dollars at retirement; the 4 percent rule and 25x multiplier work with either as long as you stay consistent. Second, the 4 percent rule already builds in annual inflation adjustments to withdrawals (you take 4 percent in year one, then index the dollar amount by CPI each subsequent year). So a 1.5 million USD corpus supports 60,000 USD in year-1 spending and approximately 80,500 USD in year-15 spending at 2 percent inflation.
Sources
- Bengen, William P. (1994) Determining Withdrawal Rates Using Historical Data, Journal of Financial Planning.
- Cooley, Hubbard and Walz (1998) Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable, Trinity University.
- Morningstar (2024) The State of Retirement Income: 2024 - updated SWR analysis.
- Fidelity Investments (2025) Retirement Health Care Cost Estimate.
- Social Security Administration (2026) Maximum monthly benefit at full retirement age.