Thread count is simply the number of threads woven into one square inch of fabric, counting both the horizontal and vertical directions. A 300 thread count sheet has 300 threads packed into that square inch. In theory, more threads means a denser, smoother fabric. In practice, the number is far less meaningful than the industry would like you to believe.
The first problem is that quality depends more on the fiber than the count. A 300 thread count sheet made from long-staple cotton will feel better and last longer than a 600 thread count sheet made from short, low-grade fibers. The length of the cotton staple determines smoothness and durability, and no amount of thread stuffing makes up for a poor fiber.
The second problem is inflation. Some manufacturers count multi-ply threads as multiple threads, so a fabric made from two-ply yarns gets its number doubled on the label. That is how you end up seeing 1,000 or 1,500 thread count sheets that feel ordinary. A genuine single-ply 1,000 thread count fabric is extremely difficult to weave; most of those eye-catching numbers are marketing math.
So what range should you actually look for? For percale, a real 200 to 400 thread count is the sweet spot, dense enough to feel substantial and smooth, breathable enough to sleep cool. For sateen, 300 to 600 is typical and gives that silky drape. Above those ranges, you are usually paying for a number, not a better night's sleep.
The honest takeaway: treat thread count as a rough guardrail, not a quality score. Once a sheet is in a sensible range for its weave, your money is better spent on verified fiber quality and construction than on chasing a bigger number.