The 4% rule is a guideline suggesting you can withdraw 4% of your pension pot in year one, then increase that amount with inflation each year, with a good chance the money lasts 30 years. On a £500,000 pot that is £20,000 in the first year.
The short answer
- The 4% rule: withdraw 4% in year one, then raise that amount with inflation each year.
- On £500,000 that is £20,000 in the first year; multiply target income by 25 for a rough pot.
- It came from US market history and was designed as a safe floor, not an optimum.
The 4% rule is the single most quoted idea in retirement income, and it is worth knowing exactly what it does and does not claim. It says that if you withdraw 4% of your pension pot in your first year of retirement, then increase that pound amount by inflation every year afterwards, your money has historically had a strong chance of lasting at least 30 years. On a £500,000 pot, that means £20,000 of income in year one, rising with prices thereafter, regardless of how markets move.
Where the rule came from
The rule traces back to US research in the 1990s, the work of financial adviser William Bengen and the later Trinity Study, which tested historical American market returns to find a withdrawal rate that survived even the worst starting years, including retiring just before a crash. Four percent was the figure that held up across almost every 30-year window. It was designed as a safe floor, not an optimal target, which is exactly why it has proved so durable as a rule of thumb.
The mechanics are worth being precise about, because the rule is often misremembered. You calculate 4% of your pot once, at the start, to set your first year’s income. After that you ignore the pot’s value entirely and simply give yourself a pay rise in line with inflation each year. So a £500,000 pot gives £20,000 in year one; if inflation runs at 3%, you draw £20,600 the next year, then £21,218, and so on, whether markets rose or fell. That deliberate blindness to the portfolio’s ups and downs is what makes the classic rule simple, but it is also its main weakness, because it never lets you respond to a bad run.
First-year income under the 4% rule (and a cautious 3.5%)
| Pension pot | 4% first-year income | 3.5% (cautious) |
|---|---|---|
| £250,000 | £10,000 | £8,750 |
| £500,000 | £20,000 | £17,500 |
| £750,000 | £30,000 | £26,250 |
| £1,000,000 | £40,000 | £35,000 |
Why UK retirees should treat it with care
The rule is a helpful anchor, but it was never a law of nature. Several things make the original 4% look optimistic for a UK investor today, which is why many advisers now start the conversation nearer 3.5%.
What the original study assumed
- US market history and US bond yields
- A fixed 30-year retirement
- Low or no investment charges
- No flexibility, spend the same whatever happens
The UK reality today
- Different returns and charges of 0.5%–1%+ a year
- Retirements that can run 35 years or more
- Fees that quietly reduce the sustainable rate
- Room to flex spending up and down each year
None of this means the idea is useless: it means you should treat 4% as a sensible opening figure and then personalise it. Lower charges let you draw more; a longer expected retirement or a cautious temperament argues for less. Flexing your withdrawals with markets, rather than rigidly increasing them every year, is one of the most powerful ways to make a pot last, as we explain in our guide to building a retirement plan. Several refinements have grown up around the original rule for exactly this reason, dynamic “guardrails” that nudge your income down after a poor year and up after a strong one, or a lower 3% to 3.5% starting rate for those planning a retirement of 35 years or more. Each trades a little income today for a much higher chance the money outlasts you.
A starting point, not a strategy
It is also worth remembering what the 4% rule quietly assumes about your other income. Most UK retirees do not rely on their pot alone, the state pension provides a large, inflation-linked, guaranteed base of around £12,000 a year, and some also have a final-salary pension on top. Because those cover a chunk of your essential spending for life, the pot only has to bridge the gap, which means the exact withdrawal rate you apply to it matters a little less than the rule’s American origins imply. That interaction is precisely why a blanket percentage should never be the whole plan.
The best use of the 4% rule is as a quick sanity check: multiply your target income by 25 and you have a rough idea of the pot you are aiming for, £25,000 a year of income points to a pot around £625,000, for instance. Turning that into a real plan, allowing for your state pension, tax, charges and your own attitude to risk, is where regulated advice earns its keep. See our how much do I need to retire guide and the wider retirement planning hub for the next steps. This is information, not personal advice, and investments can fall as well as rise.
In summary
- The 4% rule: withdraw 4% in year one, then raise that amount with inflation each year.
- On £500,000 that is £20,000 in the first year; multiply target income by 25 for a rough pot.
- It came from US market history and was designed as a safe floor, not an optimum.
- UK charges, longer lives and different returns lead many advisers to start nearer 3.5%.
- Flexing withdrawals with markets makes a pot last far longer than a rigid rule.
Sources and further reading
- Taking your pension MoneyHelper
- The new State Pension GOV.UK
- Check your State Pension forecast GOV.UK
Read the full guide
For the complete picture, see our in-depth guide: How to Build a Retirement Plan.
Speak to a vetted retirement planning specialist
This is free information, not personal advice. When you’re ready, we’ll match you with an independently vetted, FCA-regulated specialist, free, and with no obligation.
