There is a famous shortcut, and it is genuinely useful. It is also built on assumptions that are worth knowing before you bet thirty years on it.
The 25x rule
Take the annual income you want in retirement and multiply it by 25. Want 40,000 a year? You need roughly a million. That is the shortcut, and its appeal is obvious.
It is the 4% rule wearing a different hat. Withdraw 4% of your portfolio in the first year of retirement, then increase that amount with inflation every year afterwards. Multiply by 25 and you get the same answer, because 1 divided by 0.04 is 25.
Where the 4% figure came from
It comes from research into historical US market returns, testing how much a retiree could withdraw without running out over a 30-year retirement — including the worst possible starting years, which is what makes it interesting. A rule that only works in good decades is not a rule.
That history is the strength and the limitation at once. It assumes a portfolio with a substantial allocation to stocks, it reflects one country's market, and thirty years is not forty. Retiring at 55 puts you well outside what the research tested.
Treat 4% as a sanity check on the size of the problem, not as a promise about your particular retirement.
The number nobody adjusts: inflation
A projected pot of 800,000 in thirty years sounds like a solved problem. At 2.5% inflation it buys roughly what 380,000 buys today. Comfortable, perhaps — but a completely different conversation from the one the big number started.
Any retirement figure quoted without translating it back into today's money is close to meaningless, because you cannot judge whether it is enough. This is the single most common way people are misled by their own planning.
You probably need less than your salary
Retirement spending is commonly 70–80% of pre-retirement spending, and the reasons are structural rather than aspirational:
- You stop saving for retirement — often 10–15% of income that simply disappears as an expense.
- Commuting, work clothes and bought lunches go with the job.
- The mortgage may be finished.
- Children, if you have them, are usually independent.
Against that, two things rise: healthcare, and the cost of having free time. Early retirement in particular is more expensive than late retirement, because you are healthy enough to enjoy it.
Subtract what you will be given
A state pension or social security payment does not need to be funded by your savings. If you want 3,000 a month and expect 1,200 from a state scheme, your own money only has to produce 1,800 — which cuts the target by 40% at a stroke.
Find out what you are actually projected to receive rather than guessing. Most systems publish a personalised statement, and the number is frequently different from what people assume in both directions.
Working two extra years does three things simultaneously: two more years of contributions, two more years of compounding on a balance that is now at its largest, and two fewer years of withdrawals. Nothing else in retirement planning is that efficient, which is why it is worth knowing before you need it.
What to do if you are behind
Most people are, at first. In rough order of effect: work slightly longer, raise the contribution by one percent of salary every time you get a raise, check the fees on your funds, and take the full employer match if one is offered — that last one is an instant 100% return and the most-ignored free money in personal finance.
And run the projection at least once a year. A plan you set at 30 and never look at again is not a plan, it is a hope.