How many feet constitutes a home run?

Answer 1

It's 90 feet along each edge of the diamond, so a home run would be 360 feet.

If you're asking how far you have to hit a ball for it to be considered a home run, there's no answer. Anything beyond the rear fence, but the position of the rear fence varies in different parks... in fact, the distance often varies considerably within a park, with the distance just inside the foul line on either side being not the same as the distance to the center of center field. Often the left field and right field distances aren't even the same.

Answer 2

Most ballparks vary in distance to the outfield fence, but with a 90-foot basepath field, one would be hard-pressed to find a fence shorter than 300 feet from home plate.