Quality sheets can have a thread count as low as 180 threads per inch or as high as 1,000. As a rule, the higher the thread count, the higher quality the sheets.
Consumers generally assume that a low thread count of 200 or 300 means the sheet is poor quality, but that's not always true. Thread counts can be artificially inflated through techniques, such as using multiple strands per "thread," but that can actually detract from quality. Experts use the softness of the sheet, called the "hand," to determine quality as much as thread count. How long a sheet holds up is determined as much by its finish and weave as by thread count. More mechanical finishes and tighter weaves make for sheets that can have as low a thread count as 180, yet feel soft to the touch and wear well for years.