Thread count is often used as a measure of fabric quality in bed sheets and other woven textiles. It refers to the number of horizontal and vertical threads per square inch in a fabric. Generally, higher thread counts are associated with softer and more durable sheets.

However, thread count is not the only factor that determines the quality of sheets, and in some cases, an extremely high thread count can even be misleading. Here's why:

1. Type of Cotton: The quality of the cotton used is arguably more important than thread count. For instance, Egyptian cotton, Pima cotton, and Supima® cotton are known for their long fibers, which create smoother, stronger, and more comfortable sheets.
2. Fiber Quality: The length and quality of the fiber (or staple) are also critical. Long-staple fibers result in a smoother, more durable fabric than short-staple fibers, regardless of thread count.
3. Weave: The type of weave, like percale (a one-under-one-over pattern) or sateen (a one-under-three-over pattern), can affect the texture and breathability of the sheets. Percale is crisp and cool, while sateen is smoother and warmer.
4. Manufacturing: Sometimes, manufacturers inflate thread count by using multi-ply threads twisted together. For example, a manufacturer might use a 2-ply thread and then double the count, marketing the sheets as having twice the actual thread count. While this sounds like it would result in a higher quality sheet, if low-quality or short-staple cotton is used, the sheets may feel rough and be less durable.
5. Finishing Process: Chemicals may be added during the finishing process to make low-quality, high-thread-count sheets feel smoother. However, after a few washes, the chemicals will wash off, and the sheets may become rough.

A good range to consider for thread count is usually between 200 and 400. Anything above that may not necessarily equate to better quality or more comfort and could be a marketing gimmick. When choosing sheets, it's also important to consider other personal preferences, such as how the sheets feel to the touch and how warm or cool they keep you.