Grab a tape measure. Do not guess. Measure the actual glass opening—the hole you step through. Then measure the total frame width. Write it down. Tape it to your fridge. Then, when you go shopping, subtract two inches from that number just to be safe. Nothing fits perfectly. Doorways are liars.
If you’re replacing the whole door, standard rough openings are often 60.5, 72.5, or 96.5 inches wide. That half-inch is the construction industry’s way of saying "we don’t trust you to measure straight."
