Measurements alone don't make it easy to visualise how much space a new sofa or table will take up.
So take the dimensions of whatever it is you have your eye on and use them to create a "shadow" of the piece from old newspapers. All you need is a scissors, sticky-tape and patience. Tape sheets of newspaper together and cut to the dimensions you have taken. Position this where the piece will sit to get an idea of the effect on your floor space.