Consider going pro.
Skip the hassle of needing to accurately measure your interior door.
You don’t have to worry about accidentally voiding your warranty.
A pro will clean up the mess and dispose of your old door.
If you go DIY, here’s how to measure your interior door.
Measure the distance between the edge of one side of the door to the edge of the other side of the door.
Next, measure the distance between the top edge of the door to the bottom edge of the door.
Measure the width of the frame, from edge to edge, across the existing door frame. Ignore any door trim.