Whatever size bed you have, it's important to buy the correct size of sheets to ensure a snug fit. Some sheets differ in size, and even if you buy a sheet set for your size of bed, the sheets might be too large. Instead of going through the hassle of returning them and buying another, or trying to sew them smaller, you can shrink them to the appropriate size at home.
Place the bed sheets in your washing machine and run them on a hot cycle.
Remove the bed sheets from the washing machine upon completion of the cycle and place them in the dryer. Run the dryer on a hot cycle until the sheets are fully dry.
Make the bed with the bed sheets to determine if the fitted sheet and flat sheet are the correct size. If they are still too large, run them through another washer and dryer cycle, which shrinks them slightly.