The honest answer is: it depends on more than your starting balance.

Two retirees can each start with $1.5 million and get very different results. One may be fine for 35 years. Another may run into trouble much earlier. The difference usually comes from spending, inflation, market timing, and how much flexibility each person has when conditions change.

The simple version people start with

A common shortcut is:

Years your money lasts = portfolio value / annual spending

By that math, $1.5 million and $60,000 of annual spending looks like 25 years.

That is a useful back-of-the-envelope check, but it is not a retirement plan.

It ignores:

Investment growth
Inflation
Taxes
Market crashes
Changes in spending over time
Extra income like Social Security or a pension

Retirement is not a straight-line drawdown. Your portfolio is still moving while you are spending from it.

The four variables that matter most

1. Spending rate

The faster you withdraw, the shorter the runway.

If you retire with $1 million and spend $40,000 per year, that is very different from spending $70,000 per year. Even if both plans earn decent returns over time, the higher withdrawal rate leaves less room for bad years.

That is why small spending changes can matter more than people expect. A permanent $5,000 to $10,000 reduction in yearly spending can materially improve a plan.

2. Inflation

Spending rarely stays flat.

$60,000 per year today does not buy the same life 15 years from now. Even moderate inflation compounds over a long retirement. If your spending rises while markets disappoint, your plan can weaken much faster than a fixed-withdrawal estimate suggests.

3. Return sequence

Average returns are not enough.

If bad market years happen early in retirement, withdrawals do more damage because you are selling from a portfolio that has already fallen. A strong recovery later may not fully repair the damage.

This is sequence of returns risk, and it is one of the main reasons two plans with the same average return can end in very different places.

4. Guaranteed income

Social Security, pensions, rental income, or part-time work can extend your plan significantly.

The key question is not just, "How big is my portfolio?" It is also, "How much of my spending must the portfolio cover?"

If your spending need is $80,000 but Social Security covers $32,000, your portfolio is supporting the remaining gap, not the full lifestyle.

A better way to think about retirement runway

Instead of asking for one exact number, ask:

What does my plan look like in a typical outcome?
What happens if inflation stays elevated?
What happens if markets fall in the first five years?
What happens if I spend 10% more than expected?
What happens if I delay retirement by two years?

That is a much better framing than trying to force retirement into one static projection.

A simple example

Imagine a household retires with:

$1.8 million invested
Retirement starting at 65
$75,000 annual spending
$28,000 annual Social Security starting at 67
2.5% inflation

On paper, that might look healthy.

But notice the timing: for the first two years, the portfolio has to cover the full $75,000 before Social Security begins.

But the answer changes a lot depending on what happens next:

If markets are strong early, the plan may look durable for decades.
If the first three years include a deep drawdown, the portfolio may never fully recover.
If spending drifts to $85,000 instead of $75,000, the failure rate rises.
If retirement is delayed by two years, the odds can improve substantially.

The lesson is not that retirement is impossible. It is that the answer is conditional.

What to review in your own plan

If you are trying to estimate how long your money will last, focus on these:

Your annual spending need.
How much of that spending is covered by guaranteed income.
Your withdrawal rate from the portfolio.
Whether early bad markets would force painful changes.
What adjustments you would realistically make if the plan weakens.

A plan with flexibility is much stronger than a plan that only works under one narrow set of assumptions.

The mistake to avoid

The biggest mistake is treating a single projection as certainty.

If a calculator tells you your portfolio lasts to age 92, that does not mean your money lasts to age 92. It means the assumptions in that one model produced that result.

What you really want to know is how sensitive that result is:

to lower returns
to higher inflation
to higher spending
to a longer life
to bad timing

That is what separates a fragile plan from a durable one.

What a useful retirement model should show you

A good model should help you see:

A range of outcomes, not one path
Failure scenarios, not just success scenarios
The impact of changing retirement age, spending, and savings
How market timing changes your runway
How income sources reduce pressure on the portfolio

That is the difference between a hopeful estimate and a real stress test.

Pathwyze is built for exactly this question. You can model your retirement plan, test different spending levels, and see how long your money may last across a range of outcomes instead of relying on one forecast.

See what this looks like with your numbers; start free.

How Long Will My Retirement Savings Last?