The size of a cat's territory depends on a lot of things.
1) Probably the most important factor is if Otis is neutered or not.
2) Next is if there are any females in heat near you.
3) Then if you live in a rural area, where there is lots of space in between houses, cats generally have territories of several acres.
4) If you live in a more urban or suburban area where there is a higher cat population, territories get much smaller. In my neighborhood, I've noticed cats generally don't go farther than 5 houses in each direction. The males may go up to 10 houses away.
5) Then another big factor is Otis's personality â€” what motivates him to wander. . .does he like to hunt, or defend his turf, or does he like to visit other humans or other kitties. . .etc.
I'm sure there are lots of other factors besides these. I'm curious why you want to know?
Maybe you should follow him to see where he wanders. My recommendations for a healthy cat would be to at least neuter him and put ID tags on.. . and of course you know the rest of the story.