What age is appropriate for a child to walk around a neighbourhood on their own?

And is it different for a boy vs a girl?

I saw a boy who looked around 11 walking along a fairly busy road on his way back from 7-Eleven with a hot chocolate about 9am today, Saturday. Plenty of cars around. Naturally, I had no idea whether his house was the next one, or still streets away.

But I felt surprised, then realised if I’ve seen kids around that age unsupervised, they’re usually with at least one other kid, and more usually on bikes than walking.

I live in a suburb outside a fairly sizeable Australian city. It’s about 7km/4.5 miles.

What do you think?

For context, please say what country you live in, whether you live in a city/town or regional/rural, and if you’re a parent or not.