High thread count bed sheets, often called percale, are much 
advertised, but what exactly does "high thread" count mean? You 
know that it means quality and comfort, but do you know why? It 
used to be considered good to have thread count of 180-200 but 
thread counts of up to 1000 are advertised these days.. So what 
is going on? Does high thread count always mean better quality? 
Is there an optimum thread count, and if so what is it?


Thread Count 101

Cotton is a woven fabric. The number of threads used in weaving 
are counted by the square inch. For example a thread count of 
180 means a weave of 100 vertical threads per square inch, 
called the warp, and 80 horizontal threads, called the weft. 
The thickness of the thread is also a factor in this equation. 
The finer the thread the more of them there will be in one 
square inch, giving a higher thread count.  

Another thing to be aware of is ply. Two ply fabric is made by 
twisting the yarns together before weaving, whereas single ply 
uses a single thread. Using two ply yarn doubles the thread 
count. So to compare the two remember that a single ply with a 
thread count of 100 is equal to a two ply with a count of 200.  
Thread count can go as high as 800 or 1000 threads, but you can 
buy perfectly good bed linen with a thread count of 180. The 
term percale means a thread count of at least 100.

A higher thread count is not necessarily better because the 
higher the thread count the thinner and more delicate the fibers 
will be, unless it is 2 ply. Since 2 ply doubles the thread count 
this makes the cotton heavier, not necessarily what you want in 
bed sheets. 

A thread count of between 100 and 400 is really quite sufficient,
there is simply no need to pay for anything more. If you are 
buying pure linen bed sheets, rather than cotton, a thread count 
of 100 is good, since linen has thicker fibers. 

Of course a high thread count is not the only determinant of 
quality in bed linen. The treatment that the cotton fiber has 
received, for example mercerizing, and the way in which the bed 
linen is woven and finished, all contribute to the quality of 
the finished product. (Mercerizing is a chemical treatment which 
produces increased strength and a sateen finish which accepts 
dyes more readily.)

Now the only other information you will need before you buy your 
bed linen is your mattress size. Check standard bed sheet sizes 
here:  http://www.all-bed-linens.com/bed-sheet-sizes.html