Calculate fabric cut sizes quickly with this free seam allowance calculator. Perfect for quilting, sewing patterns, and garment projects.

How to Calculate Seam Allowance

When sewing fabric pieces together, seam allowance must be added to the finished size of your project. Seam allowance is the extra fabric between the edge of the fabric and the stitching line.

Because seams exist on both sides of a fabric piece, the seam allowance must be added twice to each measurement.

For example, if your finished fabric piece should measure 10 inches wide and you are using a ½-inch seam allowance, the cut width must include seam allowance on both sides.

This means:

10 inches + ½ inch + ½ inch = 11 inches

The same rule applies to the height measurement.

This calculator helps you quickly determine the correct cut size so your finished piece ends up exactly the size you want after sewing.

---

Common Seam Allowances

Different types of sewing projects use different seam allowances.

Quilting:
¼ inch seam allowance

General sewing:
⅜ inch or ½ inch seam allowance

Garment sewing patterns:
Often ⅝ inch seam allowance

Always check the pattern instructions before cutting fabric.