Learn about the differences between 30 weight and 40 weight embroidery thread
About Thread Weights
Weight refers to a thread's thickness. While it is somewhat counter intuitive, a lower weight number means a thicker thread. This means a 30 weight thread is thicker than a 40 weight thread.

Embroidery Thread Weights
The most common thread weight used for embroidery is 40 weight. Most digitizing programs are designed for using 40 weight. There are programs that can be modified to use 30 weight.

Compare
Thickness
30 Weight - Thicker and heavier. It covers more surface area in less time. 40 Weight - Thinner. It is better for finer, more detailed jobs.
Needle Size
30 Weight - Needle Size: 90/14 to 100/16 40 Weight - Needle Size: 75/11 to 80/12
Average Yards per King Spool
30 Weight - 4,400 Yards 40 Weight - 5,500 Yards
Sewing Machine Tension
30 Weight - Normally requires greater machine tension 40 Weight - Normally requires less machine tension
Denier
30 Weight - 150 / 2 (150 denier x 2 plies) 40 Weight - 120 / 2 (120 denier x 2 plies)