The F2F( floor-to-floor) width, not the length of a bed determines the size of the cover.
Bed length is generally standard across the size ranges however width varies with changing mattress depth due to toppers etc
The most important measurement you need for selecting the correct bespread size is floor-to-floor width, especially if you want your bedspread to drape to the floor.
Here's how to calculate F2F width:
Use that figure as a guide when selectng a new bedspread- the width and length should always be indicated in the product info online and on the packaging.
The standard width of a Queen bedspread, touching the floor is aprx 270cm
If you have a Queen bed that measures 265cm F2F and select a standard Queen bedspread (270cm w) it will fall aprx 2.5cm short of the floor, which is minimal.