Leather Stitching Thread Calculator (Saddle Stitch)

How it works

stitches = seam length ÷ stitch spacing · thread in the seam = stitches × 2 × (spacing + leather thickness) · thread to cut = thread in the seam × (1 + margin) + extra for needles and tie-off

In a saddle stitch one thread with a needle on each end passes through every hole twice, so each stitch uses two runs along the surface (one on each face) plus two passes through the leather. That makes the thread roughly 2 × (spacing + thickness) per stitch — about four times the seam length when the leather is as thick as the stitch spacing, which is where the common "4× the seam" rule comes from. Thick leather and fine spacing push the ratio higher, so add a safety margin and enough tail to hold both needles and back-stitch the ends.

Worked example

A 30 cm seam at 4 mm spacing in 4 mm of leather has 75 stitches; 75 × 2 × (4 + 4) = 1,200 mm of thread in the seam. Add 10% and 30 cm for the needles: cut 162 cm of thread (1.62 m), 5.4 times the seam length.

Sources: Wikipedia — Leather crafting · Wikipedia — Saddle stitch

Frequently asked questions