How is longevity calculated?

We simulate each year: the balance grows by the expected return, then the year's withdrawal (increased annually by inflation) is subtracted, until the balance reaches zero.

What is a sustainable withdrawal?

The amount you could withdraw indefinitely is roughly the balance times your inflation-adjusted (real) return — spending only real growth preserves principal.

Why does inflation matter so much?

Your spending rises every year with inflation, so even a portfolio that earns a positive nominal return can be depleted if withdrawals grow faster than real returns.

Does this guarantee my money will last?

No. It uses a fixed average return; real markets vary year to year (sequence-of-returns risk). Treat it as a planning estimate.

How can I make my money last longer?

Lower withdrawals, delay Social Security, keep some growth assets, and stay flexible in down markets.

Money Longevity Calculator

Find out how long your savings will last given your spending, expected return, and inflation — and what you could spend forever.

Your situation

Current assets

Current age

Monthly withdrawal

Expected return

Inflation

Spend-forever estimate

Withdrawing about / month spends only your inflation-adjusted growth and preserves principal.

How to Use

1
Enter your assets. Add your current investable assets and your age.
2
Set monthly spending. Enter how much you withdraw each month.
3
Set assumptions. Adjust expected return and inflation.
4
See the result. See how many years the money lasts, the depletion age, and a sustainable spend.

Calculation Method

We run a year-by-year simulation. Each year the balance grows by the expected return, then the annual withdrawal (escalated by inflation) is subtracted:

balance_y+1 = balance_y × (1 + r) − withdrawal_y
withdrawal_y+1 = withdrawal_y × (1 + inflation)

The "spend-forever" figure uses the real return (1+r)/(1+i) − 1: spending only real growth keeps the principal intact. This model assumes a constant average return and ignores sequence-of-returns risk.

Examples

Example. $750,000 at age 65, withdrawing $4,000/month, 5% return, 3% inflation: the money lasts roughly 25–30 years (into the early 90s). Spending closer to $1,200/month would be sustainable indefinitely under these assumptions.

Frequently Asked Questions

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Disclaimer: Calculations are projections based on the assumptions you provide and are for informational purposes only. They are not financial, tax, or investment advice. Investment returns are not guaranteed. Consult a Certified Financial Planner (CFP) before making retirement decisions.

Data source: Year-by-year depletion simulation with inflation-adjusted withdrawals.