Or buy the next size up in sheets.

I have an old-fashioned double bed, but bought a new thicker matress and box springs, so buying standard queen sheets works for me. My problem is that the elastic has given out on the fitted sheet. Yes, I can sew. I HATE mending. I am loath to replace the yards of elastic in the fitted bottom sheet. So I use the garter thingies to help keep the corners tucked.