The short answer is: measure your actual clear doorway opening, compare it with the bench’s smallest assembled cross-section, and check whether the bench can be partly disassembled. In many homes, a standard exterior door is around 36 inches wide by 80 inches tall, but interior doors are often only 30 or 32 inches wide. The number on the door slab is not the number you need.
First, measure your actual doorway clearance. Open the door as far as it will go and measure from the inside edge of the door stop to the face of the open door at the narrowest point. This clear opening is often 1 to 2 inches less than the nominal door width. Also measure from the floor to the top of the opening, not just the door panel height.
Next, find the bench’s assembled dimensions. Look for width, depth, and height, not just the seat width. Because you will likely carry the bench end-first through the door, the dimensions that usually matter are depth and height. For example, if an outdoor bench is 48 inches long, 25 inches deep, and 34 inches high, the cross-section you need to fit through the doorway is about 25 by 34 inches. That fits through a clear opening of 31.5 inches wide and 80 inches high. If the bench depth is 36 inches and your clear opening is 32 inches, it will not fit on the flat, and tilting should not be relied on because legs, armrests, and back edges tend to catch.
Also check whether the bench can be disassembled. Many outdoor benches have legs or backrests that unbolt. If the largest remaining piece is a flat seat board or separate side frames, the bench may pass through a much smaller opening. If you are ordering online, look for terms like “assembly required” or “knock-down construction.” If it ships fully assembled, ask for the package dimensions or plan to unbox it outside.
Remember that the doorway is only one obstacle. Measure narrow hallways, stair turns, elevator doors, and the space just inside or outside the door where you will set the bench down. A bench can fit through a door but still be impossible to turn around a tight corner. If you are unsure, cut a cardboard template at the bench’s cross-section dimensions and carry it through the path before the bench arrives.
If the numbers are close, you can often remove an interior door from its hinges in minutes to gain back an inch or two of clear opening. Protect the bench edges and door frame with moving blankets. If it still does not fit, choose a bench with knock-down parts or flat-pack delivery instead.