Choose your TV size and how it stands, pick a soundbar, and see both drawn to scale - with a warning if the bar would cover the bottom of the picture.
Width. A soundbar looks in proportion when it is about as wide as the screen or a little narrower. Wider than the TV is not wrong, but it overhangs, and on a narrow console it can stick out past the ends. The note under the drawing gives the difference per side.
Height, and the gap under the screen. This is the one people get caught by. A TV standing on feet at its ends usually leaves 1 to 3 inches between the console and the bottom of the screen; a bar taller than that covers the picture, and often the TV's remote-control sensor. A centre stand usually lifts the panel a little more. Measure yours and type it in. If the bar is too tall, the fixes are a TV stand with height settings, wall-mounting the TV, or a lower bar.
Screen sizes are the 16:9 diagonal the TV is sold by. The drawing adds a thin bezel; real bezels vary by a fraction of an inch.
Every soundbar in the list is drawn from the maker's published dimensions. Browse them all on the soundbars page, or compare any two on a soundbar comparison.