Measure before you order. Gym equipment is large, and the room it goes in matters as much as the machine.
Floor space
Each product page lists the machine's length, width and height when the manufacturer publishes them. Measure the space where it will stand and compare. Then allow clear space around it for getting on and off, and for any moving parts. The manufacturer's manual states the clearance it requires, and treadmills in particular need clear room behind the belt.
Ceiling height
Ceiling height matters most for treadmills with an incline, because the front of the machine rises, and for anything you stand on or reach above. Add the machine's maximum height from its specification to your own standing height, with your arms by your sides, and compare the result with the ceiling. If the manufacturer states a minimum ceiling height, use that figure.
Getting it into the room
Large machines arrive in large boxes. Measure doorways, hallways, stairs and tight turns on the route, and check the delivered package size against them where the manufacturer lists it.
The floor
Use a level, firm surface. Heavier machines concentrate their weight on a small area, so check the listed machine weight against the floor it will stand on. A mat under the machine protects the floor and cuts down vibration.
Folding and storage
Some treadmills and rowers fold or stand upright for storage. If this matters to you, check the folded dimensions on the product page. We only state that a machine folds when the manufacturer says so.