Can a king size bedspread be altered to a queen size?

use them as they are, unless they are hitting the floor, then hem them up.

If the pattern on the bedspreads aren't so large that they'd look obviously off kilter when shortened, then I'd say go ahead and cut them down to size.

However, before cutting anything I'd fold under the parts you plan to cut so you can see what the finished product will look like.

Sure, measure it out or depending on the pattern you may want to take all th extra material off one side so you only have to rehem one side. Not sure if the length is different as well? Then you might have a wide enough piece to make something decorative such as trimming curtains or making a throw pillow, or a dresser scarf, or whatever. Maybe even a lampshade cover depending on what the fabric is like.

I would go with discovering something new .... its a lot of work to cut down and finish a king bedspread. If you love them, cut them down into Euro pillows for the back of the bed, maybe use some of the fabric to upholster a bench at the foot of the bed.

It all turns on the pattern or print of the bedspread and what you can do with the remnants if you do cut it down.

Don't cut them! Try a french seam. Depending on how many inches you need to reduce make the seam about 1 inch each. The result looks like a Roman shade. I know, now what country do you go to, LOL. Measure up say 4 inches from the hem. Fold fabric and stitch a 1 inch seam. This takes 2 inches off the width of the spread. Repeat until you have desired width. I hope you understand this as it is a little hard to explain. Maybe google french seams?

Make sure you try the king size bedspread on the new queen mattress, before deciding what to do. . If you have not purchased a new mattress in a few years - they are a lot thicker. I have used a king size comforter on a queen bed, as otherwise it is too short to come down on the sides. It may just fit, especially if you want it to come down to the bedrails or below.