A room can have plenty of floor and still feel like an obstacle course. The usual reason is not how much furniture you own but where the gaps fall: one pinched spot between the sofa and the wall, and every trip across the room turns into a sideways shuffle. Fixing that costs nothing, because it only means sliding things around.
The plan below is a top-down view. The route runs from the door to the window. The planner finds the widest route it can, draws it, and rings the tightest spot along the way. Enter your own room size first, then drag each piece (or select it and use the arrow keys) until the tightest spot is comfortable.
Layout guides differ by a few centimetres, but they agree on the shape of the answer. A route you use every day, such as door to sofa or sofa to window, is comfortable at around 90 cm or more. A side route you only use now and then can squeeze down to about 60–75 cm. Below roughly 55–60 cm most adults have to turn sideways, and that is the point where a room starts to feel cramped however much floor it has.
A few related gaps are worth knowing:
Start with the room itself: wall to wall at floor level, because skirting boards and radiators steal a few centimetres. Then note where the door opens and how far it swings, since that arc is floor you cannot use. Write down the width of each piece you own or plan to bring in, including its depth, and check the doorways and stairs it has to pass through on the way in.
Next, mark the route with masking tape or a row of shoes. Tape the footprint of the sofa on the floor, walk the route from the door to where you actually go, and look for the spot where your hip brushes something. This takes five minutes and shows you more than any plan.
Before you buy or remove anything, try the free moves. Push the largest piece against a wall so the free floor becomes one open stretch rather than two thin ones. Turn a sofa so its short side faces the route. Swap a bulky coffee table for a small round one, or a nesting set you can slide away. Move the armchair out of the line between the door and the window; chairs love to sit right in the walkway. In a rental these changes are all reversible, and if a piece is still in the way, selling it second-hand is a perfectly good way to give the room back some space.
Numbers are a guide to comfort, not a test your home has to pass. A nook that only you use can be tighter than a hallway the whole household crosses. If anyone uses a walker, a wheelchair or a pushchair, or carries things regularly, give the main route 100 cm or more. Very small rooms often accept a slightly narrow side route in exchange for a spot to sit, and that is a fair trade if you know you are making it.
If a tight spot persists and you do decide to replace something, let the gap decide, not the catalogue. Measure the width and depth you can afford, then look for pieces with slimmer arms, raised legs that let the eye see the floor, or a smaller depth. Only buy once the taped-out footprint feels right when you walk around it.