Thread Calculator

Estimate how much thread a seam consumes from its length and the stitch type, and work out how many bobbins or spools that needs.

Seam length to be sewn in

Measure the seam line, then add every extra pass over the same length, such as a topstitch or an edge finish.

Stitch type

Each stitch class uses a different multiple of the seam length. An overlock uses several times what a straight stitch does.

Passes over the same seam passes

A sewn and serged and topstitched seam is three passes.

Thread on one bobbin yd

A domestic bobbin holds roughly 35 to 45 yd of 40 weight thread. A serger cone holds 1,000 yd or more.

Thread on one spool yd

A standard domestic spool is 100 to 150 yd. Industrial cones run 5,000 yd.

Thread weight wt

40 weight is the standard all purpose sewing thread. Lower numbers mean thicker thread.

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