Choose the width you want to see
Enter the finished size of the quilt center and the finished width of the border. Finished width is the part you'll see after the border is sewn into the quilt. The calculator adds seam allowance to the cut width and to both ends of each strip. Use the same measurement basis for the center and border.
The first pair changes the second pair
For a 40 × 50-inch center with 3-inch finished borders and ¼-inch seams, cut the strips 3½ inches wide. If you attach the top and bottom first, cut that pair 40½ inches long. The side strips then need to be 56½ inches long. Attach the sides first instead, and the lengths change to 50½ and 46½ inches.
Measure again before attaching the strips
The finished quilt in this example will measure 46 × 56 inches. Check your sewn center against the planned dimensions before cutting long border strips. This tool covers straight borders with square corners. It doesn't work out mitered corners, fabric yardage or the extra length needed to piece shorter strips together.
Carry the new size into the next calculation
Once you choose a border width, use the new finished quilt size for binding. For backing and batting, measure the completed top and add the overhang you need. Even a small change in border width can move a later fabric purchase into the next shop increment.