Count every layer in the seam.

How the estimate works

The calculation uses the conventional approximation of one leather ounce to 1/64 inch, or 0.396875 mm. Leather ounces describe a traditional weight-based thickness convention; they are not fluid ounces. A hide sold within an ounce range will vary. For a 4–5 oz range, calculate both endpoints rather than treating four ounces as an exact measurement.

The stack estimate multiplies the converted thickness by the number of equal layers, then adds your extra thickness. Use the extra field for a lining or reinforcement measured in millimeters. For unequal leather layers, convert each separately and add them before entering a total in millimeters with one layer selected.

What the number does not establish

Softness, finish, density, adhesive and compressibility all affect a real seam. This tool does not predict penetration force, feed quality or stitch formation. It does not compare the result with a presser-foot clearance to approve a machine.

A folded section may have more layers than a simple cross-section suggests. Measure the thickest intersection and check whether the work can be positioned without scraping its finish. Read Leather Thickness for Sewing: Measure the Complete Seam and Skiving Leather Before Sewing: Where to Reduce Bulk before treating a thinner seam as the only possible solution.