I Asked AI My Retirement Number Four Ways and Got Four Answers
Same household, same facts, four phrasings. The answers ran from $1,150,000 to $2,800,000. What moved them was not randomness.
Google’s AI Overview does the retirement arithmetic correctly. Every calculation it produced in this test checked out to the dollar. That turned out not to be the useful question.
The useful question is which arithmetic it decides to run, and that is set almost entirely by what your question happens to mention. Ask how much you need to spend $70,000 a year and it says $1,750,000. Mention that $24,000 of that arrives from Social Security and it says $1,150,000. Both answers apply the 4% rule correctly. They are $600,000 apart.
Which means the person who already knows that guaranteed income reduces the target gets the right number, and the person who does not know gets the wrong one. The tool is most accurate for the people who need it least.
The test
One household, kept identical throughout. They spend $70,000 a year and expect $24,000 a year from Social Security. I picked round figures so the arithmetic stays easy to follow, and a benefit of $2,000 a month so the household reads as ordinary rather than exotic.
The right answer, using the 4% rule the AI itself cites: the portfolio covers the part guaranteed income does not, which is $46,000. At 4%, that is $1,150,000.
I put that household’s question to Google’s AI Overview four different ways on 26 October 2026, then ran one of the phrasings five times to see how much the answer moved on its own. I checked every figure that came back against the arithmetic.
Four phrasings, four answers
| What I typed | Headline answer | Verdict |
|---|---|---|
| “how much do I need to retire if I spend $70,000 a year and get $24,000 from social security” | $1,150,000 | Right. Subtracted the benefit, showed the $46,000 gap, and gave a 3.5% to 5% band. |
| “how much money do I need to retire if I spend $70,000 a year” | $1,750,000 | The 25x shortcut on the whole $70,000. Social Security appears as an afterthought, several paragraphs down. |
| “how much savings do I need to retire on $70,000 per year” | $1.25M to $1.75M | Better. Led with a range and said up front that other income means “significantly less”. |
| “how much do I need saved to retire comfortably” | 8 to 12x salary | Changed method entirely, to salary multiples. Contains a contradiction, below. |
Two of those are the same question. “How much money do I need to retire if I spend $70,000 a year” and “how much savings do I need to retire on $70,000 per year” are the same sentence with different furniture. One leads with $1,750,000 and barely mentions Social Security. The other leads with a range and raises guaranteed income in its first sentence.
Nobody types their question twice. You get whichever version your phrasing happened to land on, and nothing on the page suggests there was another one.
The arithmetic was never the problem
This is worth being fair about, because the easy version of this article would claim AI cannot do the math. It can.
Every figure checked out. $46,000 divided by 0.035 is $1,314,286, which is what it printed. $70,000 divided by 0.03 is $2,333,333, which is what it printed. When I gave it the hardest version of the question, a 60-year-old retiring now with benefits starting at 67, it correctly identified that this needs a two-phase answer: seven years where the portfolio carries the whole $70,000, then $46,000 a year after that. It put the target at $1.32 million.
Our own calculator puts it at $1,318,000. That is a better answer than our calculator gave a week ago, when it subtracted Social Security from every year of retirement including the seven years before it starts. We logged that as a correction.
So the failure is not calculation. It is that the calculation has to be chosen before it can be run, and the choosing depends on facts the question did not contain.
The contradiction in the generic answer
The fourth phrasing produced the one outright error. Asked the broadest version of the question, with no figures at all, the AI Overview offered a table of methods. Its 4% rule row said this:
The rule says subtract Social Security. The example, in the same sentence, does not. $60,000 times 25 is $1,500,000, which is the figure for a household with no benefits at all.
Apply the rule as written, with the same $24,000 benefit, and you get $900,000. The instruction and the worked example sitting beside it are $600,000 apart. A reader skims the example, because that is what examples are for.
How much does it vary on its own?
Less than you would think, and less than the phrasing effect. I ran the $70,000 question five times. Four runs led with $1,750,000. One stretched to a range of $1.75 million to $2.8 million, having reached for a 2.5% withdrawal rate as its conservative end where the other runs used 3% or 3.5%.
So the answer is reasonably stable for a given set of words, which is exactly what makes the phrasing effect hard to notice. Ask twice the same way and you get the same number twice, which feels like confirmation. It is not. It is the same question.
One caveat on all of this. AI Overviews change, and they are not identical for every user. If you run these queries you may not see what I saw. That is part of the point, and it is why the figures above are quoted with the date I collected them.
What to actually do with this
Not “don’t ask AI”. It is genuinely good at this when the question is complete, and it was better than our own tool on the bridge-years case.
The practical move is to put the structure in the question yourself. A retirement question that will get a useful answer contains four things: what you spend, what arrives regardless of what your portfolio does, when that income starts, and what withdrawal rate you want assumed. Leave out the second and you will be handed the 25x number. Leave out the third and you will be short the bridge years.
And when the answer comes back as a single figure to the dollar, treat that as a presentation choice rather than a measurement. The honest version of $1,150,000 is somewhere between $1,020,000 and $1,310,000, because the withdrawal rate it rests on is a judgement that reasonable people put anywhere from 3.5% to 4.5%. The first phrasing gave that band. Three of the four did not.
Questions people ask
Can AI calculate my retirement number?
It can do the arithmetic correctly, and in testing it did. What it cannot do is know which arithmetic to run, because that depends on facts about you that the question has to contain. Asked how much is needed to spend $70,000 a year, Google’s AI Overview answered $1,750,000. Asked the same thing with $24,000 of Social Security mentioned, it answered $1,150,000. Both used the 4% rule correctly. The difference was entirely in what the question supplied.
Does Social Security reduce how much I need saved to retire?
Yes, and substantially. The portfolio only has to cover spending that guaranteed income does not. At $70,000 of annual spending with $24,000 arriving from Social Security, the portfolio covers the $46,000 gap, which at a 4% withdrawal rate is $1,150,000 rather than the $1,750,000 that multiplying all $70,000 by 25 produces. The difference is $600,000.
Do AI Overviews give the same answer every time?
Mostly, for a given phrasing. The same query was run five times and returned a headline figure of $1,750,000 in four of those runs. The fifth returned a range topping out at $2,800,000. Run-to-run variation is real but smaller than the variation caused by rewording the question.
Should I use the 25x rule to find my retirement number?
Only on the spending your portfolio actually has to fund. The 25x shortcut is the 4% rule inverted and it is sound arithmetic, but applying it to total spending assumes no pension and no Social Security. For most households that overstates the target, because guaranteed income arrives whether or not the portfolio produces anything.
What should I include when I ask an AI about retirement?
Four things, at minimum: annual spending, guaranteed income from Social Security or a pension, the age that income starts, and the withdrawal rate you want used. Omitting guaranteed income is what produces the 25x answer. Omitting the start date is what leaves the bridge years unfunded.
Retire BFF is an independent publisher, not a registered investment adviser, tax adviser, or financial planner. This article describes a test of publicly available AI search results on one date and is general information, not advice about your situation. AI Overviews vary between users and over time, so your own results may differ from those quoted here. Retire BFF has no relationship with Google.