How to use it
- Enter your age, the age you plan to retire and the age the money should last to, what you have saved and what you save each month (and how much you expect to raise it each year).
- Choose your assumptions: the yearly return before and during retirement, inflation, and the monthly income you want in today’s dollars.
- Read the balance at retirement (also in today’s dollars), the income it can sustain, and whether your target lasts; if it does not, the extra monthly saving that would make it last.
How it calculates
The calculator works month by month. Yearly rates become the equivalent monthly rates, so 6% a year compounds to exactly 6% over twelve months. While you save, each month’s balance grows and the contribution is added at the end of the month, and the contribution rises by your chosen percentage once a year. In retirement, the income you want is first converted from today’s dollars to the dollars of your retirement year, taken at the start of each month, and raised with inflation every month while the rest keeps earning the retirement return. The sustainable income solves that last phase in closed form, and the extra saving needed is exact because the balance at retirement rises in a straight line with the monthly contribution.
What we tested
On October 14, 2026 we compared the page’s own functions with an independent month-by-month model in 60-digit decimal arithmetic on 2,001 random plans (ages 20 to 105, returns from −2% to 10%, inflation 0% to 5%): every balance and run-out month matched; every sustainable income, when simulated, ended within a cent of zero; and in the 1,680 plans that fell short, adding the suggested extra saving made the money last to the final month. A version that forgot to raise withdrawals with inflation failed the test. In Chromium: the example plan showed $1,449,030 at 67 ($657,527 in today's dollars), a sustainable $2,380 a month, and that $4,000 a month runs out at about 82 unless about $700 more is saved monthly; saving $1,501 a month made it last to 95; $2,000 a month lasted to 95 with money left; the chart drew 60 yearly bars; a retirement age below the current age showed a message; the page fitted a 390 px phone with no errors.
This is an illustration built on your assumptions, not financial advice. For the compounding behind it, see the Compound Interest Calculator; for what past dollars are worth today, the Inflation Calculator.
Sources
Checked on .
Frequently Asked Questions
Built by Derek Giordano · Part of Ultimate Design Tools