How to Calculate Thread Consumption for Garments?

There is a standard formula for determining thread consumption for apparel products. In that formula, you will get multiplying factors according to machine type and stitch class. To determine thread consumption you just need to multiply seam length with those factors. This way one can estimate the total thread requirement for making a garment.

Actual thread consumption for a unit length of seam depends on the following factors. 
  1. Stitch Classes
  2. Stitches per inches (SPI)
  3. The thickness of the seam (fabric thickness)
  4. Thread tension
  5.  Thread count (thickness of sewing thread)
So you are suggested to calculate garment thread consumption by your own. You can develop a multiplying factor according to your product categories and requirement using the following steps.

Step 1: To calculate thread ratio, you need a sewing machine, fabric and sewing thread that will be used for bulk production. For fabric and thread, you can take similar thickness and same thread count in case actual is not available.

Step 2: Sew a seam of 12 cms long and take 10 cms seam out of it by trimming 1 cm from both edges.

Step 3: Unravel both needle thread and bobbin thread from the seam. Remove crimp from the unraveled thread and measure its length in cm. Generally, it will be higher than the seam length. Now find the multiplying factor by dividing thread length with seam length. Assume unravelled needle thread length is 12.5 cm then needle thread multiplying factor is 12.5/10 or 1.25.
Using this method you can find out any types of machines’ thread consumption factors.

Step 4: Once you have consumption factors then it is easy to calculate total thread consumption. Measure the seam length of all operations of the garment and get thread requirement by multiplying thread consumption factor. Add thread wastage 5% for the thread that trims out from each end of the seam.

For quick reference, you can follow the following thread consumption ratios. Source: Coats thread consumption guide.
Thread consumption ratio

If you want to refer ready-made thread consumption factors then refer to Coats and A&E's Technical bulletins.

You may also like: Sewing Thread Consumption Calculation Template (Download Excel Template)

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