Depends on how far apart the bases are on the basepaths. It's a right triangle so the sum of the squares of the distance between first and second and from second to third should equal the square of the distance from first to third. if the bases are about 90 feet apart the distance is about 127.3 feet. Of Course, if you follow the basepaths the distance is 180 feet. And you thought you'd never use geometry in real life!
In little league, where the bases are 60 feet apart, the distance between first base and third base is 84.85 feet. In MLB and leagues where the bases are 90 feet apart, the distance between first base and third base is 127.29 feet.
According to MLB.com, "the distance between first base and third base is 127 feet."
84 Feet 10 inches
The distance between 1st base and 3rd base on a MLB field is 127'.
According to MLB Rule 1.04: "The distance between first base and third base is 127 feet, 3.38 inches."
The distance between first and second base is 90 feet. And from second to third is 90 feet, and from third to home is 90 feet.