Standard hospital beds use sheets that are 36 inches by 80 inches. Since hospital beds have extra-long twin-size mattresses, they need special hospital bed sheets, not standard twin-size sheets.
It is important to know how thick the hospital bed mattress is before buying sheets. Some sheets are made to fit beds that are only nine inches thick, but some hospital beds are 12 inches thick. Since fitted sheets have elastic, a sheet for a hospital bed that is 12 inches thick also fits beds that are less thick. Specialty beds, such as those used for bariatric surgery patients, are larger and require special sheets. Also consider whether woven or knitted sheets are more desirable.