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The 4% rule, tested against CPF LIFE and Singapore lifespans

Updated 1 October 2026

The 4% rule is the most quoted number in retirement planning. Take 4% of your savings in your first year of retirement, raise that amount with inflation every year after, and your money should last.

It's a useful starting point. It's also American, built on American data, for a retirement that looks different from yours. This post explains where it came from, then runs it against Singapore's numbers.

Where the rule came from

In October 1994, a US financial planner named William Bengen published a paper in the Journal of Financial Planning called "Determining Withdrawal Rates Using Historical Data."

He took historical returns on US shares and bonds and asked a simple question. If you'd retired in any year in that history, what was the highest starting withdrawal that would have lasted about 30 years, with the amount raised for inflation each year? The answer in the worst historical periods was a little over 4%. Bengen later called this the "safe maximum" rate, and it became known as the 4% rule.

Three things are baked into that result:

  • US market history, which was a strong one by world standards
  • A retirement of about 30 years
  • No other income in the calculation, just a portfolio and withdrawals

Each of those changes when you live in Singapore.

What's different here

The biggest difference is CPF LIFE. Most Singaporeans born in 1958 or later can get a monthly payout for life from 65. So you aren't funding your whole retirement from a portfolio. You're funding the gap between CPF LIFE and what you spend.

That changes the maths. Here's an illustration.

Running the numbers

This is an illustration with made-up spending and simple assumptions. It isn't a forecast or a recommendation.

Take someone who turns 55 in 2026 with the Full Retirement Sum of $220,400 in their Retirement Account. CPF estimates their payout at about $1,780 a month from 65 on the Standard Plan.

Say they want $3,000 a month in today's money. The gap is $1,220 a month, or $14,640 a year.

Applying the 4% rule to that gap, they'd need $14,640 divided by 4%, which is $366,000 in savings at 65.

Now test it. Our assumptions:

  • Withdrawals are taken at the start of each year
  • Prices rise 2.5% a year
  • The savings earn a steady 3%, 4% or 5% a year, with no bad years and no fees

First, the rule as Bengen framed it: take $14,640 in year one and raise it by 2.5% a year.

Yearly return on savingsSavings last about
3%26.6 years
4%30.8 years
5%37.5 years

Those figures look comfortable. They leave out how the Standard Plan behaves over time.

The catch: a flat payout and rising prices

The Standard Plan pays the same amount every month. Your spending doesn't stay the same. At 2.5% a year, $3,000 of spending today becomes about $3,840 a month after 10 years and $4,916 after 20.

CPF LIFE still pays $1,780. So the gap your savings must fill isn't growing at 2.5%. It's growing faster: from $1,220 a month to about $2,060 after 10 years and $3,136 after 20.

Rerun the same $366,000 with that growing gap:

Yearly return on savingsSavings last about
3%20.3 years
4%22.2 years
5%24.8 years

From 65, that's savings running out somewhere between 85 and 90. Remember these figures assume steady returns. Real markets have bad years, and a bad run early in retirement shortens these figures further.

Then compare with how long people live

In 2025, a Singapore resident aged 65 could expect to live another 21.6 years on average. For women it was 23.1 years, for men 19.9. Those are averages, so many people will live well beyond them.

Put that next to the second table. In the middle case, the savings run dry at about 87. That's close to the average lifespan, which means a large share of people would outlive the money.

CPF LIFE itself keeps paying however long you live. The part of your income that can run out is the part coming from your own savings.

So does the 4% rule work in Singapore?

As a rough first estimate of how much savings you need on top of CPF LIFE, it's a reasonable place to start. As a plan, it needs adjusting:

  • Apply it to the gap after CPF LIFE, not to your total spending
  • Account for how your CPF LIFE payout behaves over time. The Escalating Plan starts lower but rises 2% a year; the Standard Plan stays flat.
  • Plan for longer than 30 years if you retire before 65, or if your family tends to live long
  • Don't rely on steady returns; keep near-term spending out of the market

Some people also look at raising the floor itself. You can defer CPF LIFE to as late as 70, which raises the payout by up to 7% for each year you wait. Or you can top up your Retirement Account up to the Enhanced Retirement Sum before payouts start. Either one enlarges the part of your income that can't run out, and either one leaves you with less money you can reach.

What to work out for yourself

The useful version of this exercise uses your numbers, not ours. You need your CPF LIFE estimate, your real monthly spending, your savings outside CPF, and when you plan to stop work.

A Financial Consultant can run that with you, with the assumptions written down where you can see them. Book a free retirement review when you're ready.

Sources