Sir David Attenborough’s 100th birthday celebrations received extensive media coverage in May this year. Centenarians are, to use Attenborough terminology, a rare breed; but how rare?

The last time the Office for National Statistics (ONS) examined the question was 2023, when it estimated there were 16,140 centenarians in the UK, more than double the number in 2003. Unsurprisingly, female centenarians outnumbered their male counterparts by 4.5 to 1. However, the number of male centenarians has been increasing at a faster rate than females; in 2003 the women outnumbered the men by 8.6 to 1.

A man aged 40 today has roughly a 1 in 20 chance of becoming a centenarian, whereas a 40-year-old woman has a 1 in 10 chance.

Coincidentally, shortly after Attenborough celebrated his birthday, the ONS issued its latest biennial update on life expectancy in the UK and refreshed its online life expectancy calculator. If you want to know how long on average the ONS projects someone of your age and sex will live, the calculator provides one simple number, with no decimal places to worry about. But it’s an answer that needs treating with care, as it’s an average for the UK population and, by definition, about half of the population will outlive the average.

Alongside life expectancy, the calculator also gives your probability of matching Attenborough’s 100-year achievement and, more realistically, reaching age 90. For example, a man aged 40 today has roughly a 1 in 20 chance of becoming a centenarian, whereas a 40-year-old woman has a 1 in 10 chance. For 90, the corresponding figures are roughly 1 in 2.5 and 1 in 2.

If those odds surprise you, then you might want to revisit your retirement planning to ensure that you do not outlast your retirement fund. After all, very few of us in our 90s will be able to supplement our pension income with royalties and fees from nature documentaries…