Will my retirement savings last? Read two answers, not one
This tool gives a steady-return answer and a simulated one, and they often disagree. Here's the default plan at different spending levels: age 35, retiring at 67, with $2,400 a month of Social Security from 67.
| Monthly spending | Steady returns | Left at the end | Simulated success |
|---|---|---|---|
| $3,000 | Lasts through 92 | $1,751,118 | 100% |
| $4,000 | Lasts through 92 | $1,288,992 | 93% |
| $5,000 | Lasts through 92 | $826,865 | 71% |
| $6,000 | Lasts through 92 | $364,738 | 50% |
| $7,000 | Runs out at 90 | Nothing | 34% |
Look at $6,000 a month. The steady line says the money lasts, with a balance left over. The simulation says it works in 50% of paths. The gap has a simple cause: returns that swing compound at less than their average. A 7% average with 12% swings compounds at about 6.3% in this model, and a retiree who is withdrawing can't wait out a bad stretch.
Is this in today's dollars or future dollars?
The headline and charts use today's dollars, and the year-by-year table uses future dollars. So the same savings at 67 appear as $2,607,837 in one place and $1,183,360 in another. The second figure is what it would buy at today's prices.
Spending works the same way. You type $5,000 in today's dollars, and at 2.5% inflation the tool treats that as $11,019 a month by 67. Comparing a future-dollar balance against today's spending makes a plan look better than it is.
Inflation also deserves a test of its own, because this field doesn't move your returns. Raise it one point and savings at 67 shrink to $867,340 in today's dollars, while the success rate falls to 41%. The inflation calculator shows what past price rises did to a dollar.
How much can I withdraw? The 4% rule and where it stops
The 4% rule says you can take 4% of your savings in year one, or $40,000 from $1,000,000, then raise that dollar amount with inflation each year. It comes from a 1994 study by planner William Bengen, who tested US stock and Treasury returns for retirements starting each year from 1926 to 1976.
In his 50/50 stock and bond portfolio, 4% never ran out in under 33 years. At 4.25%, one portfolio ran out in 28. Up to about 3.5%, it lasted at least 50 years every time.
| Savings | 3% | 3.5% | 4% | 5% |
|---|---|---|---|---|
| $500,000 | $15,000 | $17,500 | $20,000 | $25,000 |
| $750,000 | $22,500 | $26,250 | $30,000 | $37,500 |
| $1,000,000 | $30,000 | $35,000 | $40,000 | $50,000 |
| $1,500,000 | $45,000 | $52,500 | $60,000 | $75,000 |
| $2,000,000 | $60,000 | $70,000 | $80,000 | $100,000 |
- It's a finding about the past. It used one country's markets, and later decades can differ.
- It targets about 30 years. Retiring at 50 asks your money to last longer, and Bengen himself suggested no more than 4% for early retirees.
- It applies to the starting balance. You don't recalculate 4% each year.
- It ignores your choices. It assumes the same real spending in good and bad years. Cutting back after a bad start isn't in the math.
In this calculator, the Withdrawal rate field only sets the "Income from savings" figure. Whether your money lasts depends on your spending field, so changing the rate won't change the age your savings run out.
How long will $1,000,000 last in retirement?
At $3,333 a month, the 4% pace, $1,000,000 lasts 39 years on steady returns of 5% with 2.5% inflation. Spending rises with inflation in every row. Tax and market swings aren't included, and they'd shorten these figures. Social Security isn't either, and it would extend them.
| Monthly spending today | How long it lasts |
|---|---|
| $3,000 | 46 years |
| $3,333 | 39 years |
| $4,000 | 29 years |
| $5,000 | 21 years |
| $6,000 | 17 years |
| $8,000 | 12 years |
Social Security: use your own estimate and match it to your claim age
Get your number from a my Social Security account at ssa.gov, because the calculator won't adjust it for you. If you change "Social Security starts at" from 67 to 70, you must also change "Social Security per month" to the amount for 70.
| Claim at | Monthly benefit | Change |
|---|---|---|
| 62 | $1,680 | -30% |
| 65 | $2,080 | -13.3% |
| 67 | $2,400 | Full benefit |
| 70 | $2,976 | +24% |
Two more things change what you'll really receive. First, tax: under IRS Publication 915, up to 85% of benefits can be taxable, depending on your other income. Second, funding: the 2026 Trustees message projects the retirement trust fund pays 100% of scheduled benefits until late 2032, then 78% from continuing income unless the law changes. That's a projection, not a promised cut. Entering 78% of $2,400 lowers the default plan's success rate from 71% to 60%, which is a fair stress test.
What is sequence-of-returns risk?
It's the danger that bad years come early, while you're withdrawing, so the same returns can leave you broke or comfortable. Take a hypothetical $1,000,000 with a first-year withdrawal of $45,000, raised 2.5% a year for 30 years. Retiree A loses 20%, 10%, and 5% in years one to three, then earns 7% for 27 years. Retiree B gets those same returns in reverse.
- Without withdrawals, both end at $4,250,285. Order doesn't matter.
- Retiree A runs out of money in year 19.
- Retiree B ends with $929,726.
Selling investments after a drop leaves fewer shares to recover. That's why the first decade of retirement carries so much weight, and why the "Range of outcomes" chart is worth more attention than any single line.
How to read the success rate, and what this model leaves out
The success rate is the share of 500 simulated market paths where your money never hit zero before your "Plan through age." A 71% result means 353 paths made it, in this model, on your assumptions. It isn't your personal odds.
- There's no official passing score, and 100% isn't a promise. It only means no modeled path failed.
- A failed path may run out at 91 or at 75. Check the 10th percentile line to see which.
- Every path assumes you keep spending as planned. You could adjust, so treat a low score as a reason to change the plan, not a forecast of going broke.
- Returns follow a smooth statistical curve with the volatility you set, cut by 30% after you retire. Real crashes can be worse.
The model also uses one flat tax rate and leaves out healthcare shocks and required distributions. It doesn't cap "You save each month" at IRS limits, so check those with the 401(k) calculator and IRA calculator. For a plan near retirement, a fee-only fiduciary adviser can test what this can't. Tax Counseling for the Elderly offers free help with pension and retirement tax questions from age 60, and a State Health Insurance Assistance Program gives free Medicare counseling.
Common questions
How much money do I need to retire?
A quick estimate is 25 times the yearly gap your savings must fill. For $5,000 a month of spending, 12% tax, and $2,400 of Social Security, that's about $984,545. How much do you need to retire? walks through each step.
What is the formula behind this retirement calculator?
Each retired year, withdrawal = spending ÷ (1 − tax rate) − Social Security − pension, with every amount raised for inflation. The balance then grows at your return, with half the year's withdrawal counted as taken mid-year. If the balance can't cover the withdrawal, that's the age your money runs out.
How much monthly income will my savings give me?
The "Income from savings" figure applies your withdrawal rate to savings at retirement, in today's dollars. The default plan's $1,183,360 at 4% gives about $3,945 a month before tax, on top of Social Security.
Does this work for couples?
Partly. Enter combined savings, spending, and Social Security. The tool models one set of ages, so it can't handle spouses retiring or claiming at different times, or the drop in income when one spouse dies. Run a few versions to see the range, and use the later "Plan through age" of the two of you.
Can I include a pension, including a military or state pension?
Yes. Enter it in today's dollars under "Pension per month." It starts at retirement. Check the cost-of-living field, since a pension with no raises loses value: $2,000 a month buys only $1,221 of today's goods after 20 years at 2.5% inflation.
Does it count my 401(k) and employer match?
Yes. Enter all your retirement savings as one balance and your monthly savings under "You save each month." The match rate and match limit are in the advanced fields. It treats everything as one pot, without separate rules for each account type.
Sources
- Determining Withdrawal Rates Using Historical Data (William P. Bengen, 1994, reprinted 2004) · Journal of Financial Planning
- 20 CFR 404.409: What is full retirement age? · Code of Federal Regulations, via Cornell LII
- 20 CFR 404.410: How does SSA reduce my benefits when my entitlement begins before full retirement age? · Code of Federal Regulations, via Cornell LII
- 20 CFR 404.313: What are delayed retirement credits? · Code of Federal Regulations, via Cornell LII
- Publication 915: Social Security and Equivalent Railroad Retirement Benefits · Internal Revenue Service
- A Message to the Public: 2026 Trustees Reports · Social Security and Medicare Boards of Trustees, via U.S. Treasury