How to calculate thread length?

This is not an issue, just a question I couldn’t find an answer to. I would be really thankful if someone can provide some help with this. I’m trying to come up with a formula to calculate the thread length needed for a pattern. I tried the distance formula between 2 stitches ( d = sqrt(a^2 + b^2) ) :

file = "../assets/e4-1053.DST"
pattern = pyembroidery.read(file)

distance = []
for i in range(0, len(pattern.stitches)-1, 1):
    if pattern.stitches[i][2] == pyembroidery.STITCH:
        a_x = pattern.stitches[i][0]
        a_y = pattern.stitches[i][1]
        b_x = pattern.stitches[i+1][0]
        b_y = pattern.stitches[i+1][1]
        d_x = a_x - b_x
        d_y = a_y - b_y
        distance.append(math.sqrt(pow(d_x/10,2) + pow(d_y/10,2)))

threadlen = sum(distance)
print(threadlen)

the result for this example is about 19.2m

I know this is missing the distance the thread has to travel at each stitch point passing through the fabric, but the result is way too far off compared to what I get when I open the same file in Wilcom truesizer where I get 55m.

What am I missing?

[tatarize]

I think wilcom’s equation is something like total_length * 1.375 + 2 * thickness * stitches. It seems to be about 37-38% longer than the raw distance. I’m guessing because material floof or they actually measured it and took the average additional length such things did. Since the thread isn’t perfectly taught.

[tatarize]

I would assume wilcom probably actually measured it. And made a pretty good guess. Comparing it to other software is likely fine but the real gold standard should be comparing it to how close it actually comes to being correct with those lengths. If you run a 200m spool, does it die where that estimate suggested it would? Etc.