Purchase a properly sized bed sheet to ensure it is tightly fitted to the bed. Sheets are manufactured with exact dimensions to fit different mattress sizes. Look at the packaging before buying to determine the sheet's size.
The most common mattress sizes are twin, full, queen, king and California king. Although a single mattress size will have the same flat dimensions amongst different brands, depth will vary. Take note of the mattress' size and depth before shopping. Fitted sheets range from 13 inches to 22 inches in depth. Besides purchasing the proper size, another tip when sheet shopping is to buy sheet suspenders, which will keep the sheet from moving or coming off the mattress. A properly fitted sheet will hug the mattress snugly and be difficult to pull off.