The (2026) NFHS Softball, Rule 7-4-8 dictates a batter is out when hitting the ball while either foot is completely outside the batter's box or touching the plate.

The rule make no distinction about anything to do with feet in the air, your wrong. Also, the ENTIRE foot has to be out of the box. By definition, if ANY part of the foot, even the smallest part of the heal is ON THE LINE, they are in the box.

NCAA (2026) 11.15.1 An illegally batted ball occurs when the batter contacts the pitch and: ANY part of their body is touching home plate OR the ground outside the lines of the batters box.

In summary, NFHS you are in the box if only PART of your foot is on the line. For NCAA, your ENTIRE foot has to be on the line.