Since beds come in different sizes, so do the sheets covering them. Sheet sizes are determined by the length and width of the bed and come in the following categories: twin, double, queen, king and California king. These sheet sizes are seen throughout the industry.

Sheet sizes are fairly standard except for the "pocket" measurement on fitted sheets. This tells the shopper how "deep" the sheet is, in case he or she has an extra thick mattress, or one with a pillow-top. So, if a shopper has a thick mattress, he or she can look for a deeper pocket, ensuring the sheet will be a good fit.

As a rule, sheet sizes are (for fitted sheets): 39 inches (99 centimeters) wide by 75 inches (191 centimeters) long for a twin sheet; 54 inches (137 centimeters) wide by 75 inches (191 centimeters) long for a double sheet; 59 inches (150 centimeters) by 79 inches (201 centimeters) for queen size beds; 80 inches by 80 inches (203 centimeters) for a king sheet; and 72 inches (183 centimeters) by 84 inches (213 centimeters) for a California king. A shopper can expect sheet sizes to be 20 to 30 inches (51 to 76 centimeters) longer and wider for the fitted sheets in each size.

Sheet sizes are standardized because mattress sizes are the same in every store. A shopper has to be able to check sheet sizes with confidence in any store and know the sheet sizes will accommodate her beds when she gets home with the linens.

Sheet sizes, thread count and quality determine bedding prices. Since thread count usually denotes a higher quality sheet, this is a good comparison feature among brands. Obviously, the larger the sheets, the higher the price. The higher the thread count, the higher the price, as well.

A shopper can get a decent set of twin sheets, as for a dorm room, for as little as $25 US Dollars (USD). A double sheet set may be $40 or $50 USD. However, prices can go up to as much as $500-600 USD for high thread counts and a designer label for king size sheets. However, shoppers can compare sheet sizes, prices and thread counts all across the Internet so she can make sure she is getting the best deal.