Looking for sheets with a reasonable thread count (200-600 for most styles) will typically produce the best results. Be sure to modify your expectations somewhat depending on the material used. Excessively high thread counts (600-800) likely won't change much beyond the price tag.
Is a 400 thread count good?
The idea is the finer threads you can weave together, the softer and finer the fabric. ... According to Consumer Reports, a thread count of 200 is fine; 400 may be softer. But anything above 400 will likely only provide a higher price tag [source: Consumer Reports].
Is a 300 thread count good?
Also, for good-quality bedding, look for a thread count between 180-300. Anything higher than a 300-thread count means the sheets and duvet covers will start to feel heavier. ... The best thread count for sheets is around 200-300.