"How long will my money last in retirement?" is one of the most common questions people type into Google the year they retire — and one of the most common answers is a vague guess. The real answer isn't a single number. It's the result of four things working against or with each other: what you've saved, what you spend, what your money earns, and how fast prices rise.
The four numbers that decide the answer
Every "how long will my retirement money last" calculation, however complicated it looks, comes down to these:
- Starting balance — what you actually have saved today.
- Withdrawal rate — how much you take out each month, relative to that balance.
- Investment return — how much your remaining balance grows while it sits invested.
- Inflation — how much more your same lifestyle will cost next year, and the year after.
Change any one of these and your answer moves — sometimes by a decade or more. That's why two people with the identical amount saved can get wildly different answers to "how long will my money last."
How long will $500,000 last in retirement?
At a 5% annual return, 3% inflation, and $3,000 withdrawn per month, $500,000 lasts roughly 20–25 years — enough to cover a retirement starting at 65 comfortably into the mid-80s. Drop monthly spending to $2,000 and the same balance can stretch past 35 years. Push spending up to $4,000 a month and it can run out in well under 15.
How long will $1 million last in retirement?
The same logic scales up: at a similar 5% return and 3% inflation, $1 million spent at $4,000–$5,000 a month typically lasts 25 to 35+ years. The starting balance matters less than people assume — the withdrawal rate does most of the work.
The mistake that skews most quick estimates
Most rough, back-of-napkin answers to "how long will my money last in retirement" assume your spending stays flat. It doesn't. If you're spending $3,000 a month today, inflation at 3% means you'll need roughly $5,400 a month for the same lifestyle in 20 years, and over $7,200 in 30. A calculator that doesn't increase your withdrawal every year is quietly overestimating how long your money will actually last — sometimes by five or more years.
What a more accurate retirement calculator does differently
- Compounds your return and withdrawal month by month, not with a single simplified formula
- Increases your withdrawal amount every year to keep pace with inflation
- Shows you a year-by-year balance, not just a single "you're fine" or "you're not" verdict
So, how long will your retirement money last?
Run your real starting balance, spending, return assumption, and inflation rate through Disaa's retirement calculator above — it simulates the same way, month by month, and gives you an exact age rather than a rule of thumb.
The gap between a good and a bad answer usually isn't the starting balance. It's whether inflation was factored in at all.