Retirement Calculator

Worked example

$150,000 saved and $800 a month more for 20 years at 6.5% reaches $940,804. By then 3% inflation has turned $4,500 of monthly spending into $8,128 and $2,000 of Social Security into $3,612, so $4,515 a month has to come from savings — which lasts 20.0 years at a 4.5% return. The 4% rule would have allowed $3,136 a month, making this plan $1,379 a month heavier than that benchmark.

How to work it out yourself

1. 1.Enter spending in today’s money, not a guess at future prices. The calculation inflates it for you, and it inflates Social Security with it, because benefits are indexed to wages before claiming and to prices after.
2. 2.A result of 99 years means the withdrawal is smaller than what the pot earns after inflation, so on these assumptions it never runs out.
3. 3.The 4% line is the rule of thumb from the retirement-withdrawal literature: draw 4% of the starting balance in year one, then raise it with inflation. It is a rough safety check on the number above, not a second opinion.
4. 4.Nothing here models tax on withdrawals, market crashes, or care costs late in life. Each of those shortens the answer, and the first two by more than most people expect.

The formula

1. What today’s savings grow to150000 * pow(1 + 0.0054167, 240)
2. What future contributions grow to800 * (pow(1 + 0.0054167, 240) - 1) / 0.0054167
3. Savings at retirement548467.01 + 392336.74
4. The same spending, in retirement-year dollars4500 * 1.8061112
5. Social Security and pensions, in the same dollars2000 * 1.8061112
6. What the savings have to cover each monthmax(0, 8127.5006 - 3612.2225)
7. Years the savings lastmax(0, -log(1 - 0.0012056 * 940803.75 / 4515.2781) / log(1 + 0.0012056) / 12)
8. What the 4% rule would allow a month940803.75 * 0.04 / 12
9. Monthly gap against that rule4515.2781 - 3136.0125

Source: US SEC Investor.gov — retirement planning, Social Security Administration — benefit calculators, US Bureau of Labor Statistics — Consumer Price Index

Questions people actually ask

How much do I need to retire?

Enough that the withdrawal line above stays under about 4% of the pot a year. On $4,500 a month of spending with $2,000 coming from Social Security, that means covering $2,500 a month from savings — around $750,000 in today’s money, before tax.

Why does the answer change so much when I move the return by one point?

Because it compounds twice: once over the years you save and again over the years you spend. A point of return over 20 years of saving is roughly a fifth more capital, and in drawdown it is the difference between a pot that shrinks and one that holds.

Should I count my house?

Not in the pot. A home you live in pays no income and cannot be spent a month at a time. It belongs in the plan as a fallback — downsizing, or a reverse mortgage — rather than as savings.

What return should I assume after retiring?

Lower than before. A portfolio being drawn from is usually shifted toward bonds, and a bad sequence of early returns does permanent damage in a way it does not while you are still contributing. The default here is two points below the accumulation rate for that reason.

Related

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• Roth IRA CalculatorWhat a Roth IRA grows to, how much of that balance is growth the IRS never taxes, and what the same money would be worth in a taxable account.
• Annuity Payout CalculatorThe monthly income a lump sum pays out over a fixed number of years at a given return, and how much of that income is interest rather than your own capital.
• Pension CalculatorA defined-benefit pension from years of service and final salary, with the age-62 multiplier cliff and the early-retirement reduction both priced.
• Investment CalculatorWhat regular contributions grow to over time, with the inflation-adjusted figure beside the nominal one.
• Estate Tax CalculatorWhether an estate owes federal tax at all, using the 2026 exclusion of $15,000,000 a person, and what the 40% rate costs on anything above it.

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