The retirement number we don't have

I’m 47, and everyone I know has a number. Everyone has thought about the number they need to retire.

In my college WhatsApp groups, many folks are working out theirs. The ones who aren’t vocal about it have been doing it quietly. One million. Two million. Five. Ten. There are calculators for it, threads about it, and a lot of confident disagreement. People trade the figures like scores.

All of that treats money as the whole and often only game. Hit the number and you’re safe. It’s half the story at best, and it happens to be the half that’s easy to measure.

In the last year or so, as I hit my mid-40s, I started thinking more about the number I actually want. Not how long can I live. Not longevity. But how long can I move, think, and look after myself without quietly outsourcing my life to somebody else?

That’s the number I care about more, and nobody in my groups is arguing about it. I wanted that as an age. One number. Independent until 85. At least as long as my Dad managed on his own. I spent a while trying to build it.

You can’t have it.

I tried anyway. The answer moved by more than twenty years depending on assumptions I had to invent. That isn’t a finding. It’s a guess with a decimal point on it.

What you can have instead

Turn it around. Don’t ask what age you lose your independence. Ask what you need today to be on track for one.

Pick 85. Find the level of some capacity below which people stop managing on their own. Work back through the rate it declines. What comes out is a number you can check this afternoon.

The tests are ordinary. Stand on one leg with your eyes open. Get down to the floor and back up without putting a hand down. Walk a measured stretch at your normal pace. Stand out of a chair five times. Count your push-ups. Take your pulse, measure your waist. Two more outdoors if you own a watch that reads heart rate.

Nothing to buy and nothing to book. A chair, a tape measure and a patch of floor. Every one of them has published numbers behind it for someone your age and sex, and some of those numbers are a great deal better than others.

Walking speed is the one with the most behind it. 1.20 m/s is roughly what it takes to cross a road on the signal. To still be above that at 85, a 47-year-old man needs 1.63 m/s today. The published median at 47 is 1.43.

Gait speed: Bohannon & Williams Andrews, Physiotherapy 2011. 23,111 people across 41 studies. Crossing threshold: Western et al, Age Ageing 2025.

So the average 47-year-old man is already behind. Not ill. Not diagnosable. Nothing a doctor would raise at a physical. Just behind. And nobody tells you, because “normal for your age” is the only feedback you ever get, and it isn’t the same claim as “on track”.

I myself liked thinking about the financial number for half of my life. You play the game and you save the earnings. Independence is not something we gain. We lose it with age. That’s the difference. But it’s the one that decides whether the first was worth the trouble.

Fifteen minutes, a chair and a tape measure.