Thread count is important when making quilts because if the thread count is too low the fabric is too lightweight for quilting as the fabric will unravel easily when handled, the fabric will shrink more, and will not last through years of wear. If the thread count is too high the fabric can be difficult to needle and can create puckering.
The ideal thread count for quilting is 68 X 68 threads per square inch. Thread counts below 60 X 60 threads per square inch are too lightweight.
For an even weave the thread count is the same in both directions. Sometimes the thread count can be found on the end of the bolt of fabric. When it is not, you can check the thread count yourself. The back of the fabric is usually easier to see the threads. Measure 1/2” of fabric and count the threads. I use a straight pin to count them. Multiply by 2 to get an full inch of threads. Do this in both directions. Keep a small measuring tape and magnifying glass in your purse when shopping...it makes counting the threads much easier.
I just puledl 6 fabrics out of my scrap bin to see what the counts were and I could guess the counts after just a couple of tries. Easy enough to do. My counts were between 68 X 68 to 76 X 76. Before long you will be able to guess the thread count of a fabric by handling it for a couple of seconds.