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SewnCake Sewing Tool

Boxed Corner Calculator

Tell us the finished depth you want for your bag or pouch, and SewnCake will show you the corner square to mark and cut.

1. Choose your finished depth

Units
Seam allowance
Method: cut equal squares from the two bottom corners, then sew the boxed corner seam. For this calculator, the corner square is based on half of the desired finished depth.
Visual cutting guide

Mark the corner square

Not to scale
Boxed corner square cutting guide A fabric rectangle with a square marked at the bottom corner to create a boxed bag corner. Bag panel 2" × 2" 2" 2" mark + cut
Cut the same square from both bottom corners of each matching panel.

2. Your boxed-corner measurement

Corner square to mark & cut
2" × 2"
For a 4" finished depth, mark a 2" square at each bottom corner.
Desired finished depth4"
Square from each corner2" × 2"
Selected seam allowance⅜"
Important: boxed-corner tutorials use more than one construction method. This tool follows the common square cutout = finished depth ÷ 2 method when the side, bottom and boxed-corner seams use the same seam allowance.