Checking Whether Furniture Will Actually Fit Before You Buy It
Measuring the room's actual usable floor space (accounting for doorways, existing fixtures, and necessary walking clearance), then comparing that against the furniture's full footprint including any clearance needed to use it properly (a chair needing room to pull out, a door needing room to open) gives a much more reliable fit check than comparing raw room dimensions against raw furniture dimensions alone.
"Will it fit" is really two separate questions — will the furniture's footprint fit in the available space, and will there be enough room left over to actually use both the furniture and the room properly.
Measuring usable space, not just total room area
A room's total square footage includes space taken up by doorways, existing fixtures, and necessary walking paths — the actual usable space for new furniture is smaller than the raw total area, and confusing the two is a common reason furniture that "should fit" based on total area doesn't actually work once placed.
Accounting for furniture's full functional footprint
A furniture item's footprint isn't just its static dimensions — a dining chair needs room to pull out and be sat in, a door (on a cabinet or an entry) needs clearance to open fully, and a walkway needs to remain genuinely walkable, not just technically unobstructed by a few inches — measuring for this full functional footprint, not just the item's resting dimensions, avoids a technically-fits-but-doesn't-really-work situation.
A practical verification method
Using painter's tape on the actual floor to mark out a prospective furniture item's full footprint (including clearance needs) before purchasing gives a much more concrete, physical sense of whether it will actually work in the space than mentally visualizing dimensions from a tape measure reading alone.