About this tool
Quilt Binding Calculator works out how much fabric to cut for the binding that finishes a quilt's edges. Enter the quilt's width and length, the width you cut your binding strips (2.5 inches is common for double-fold), your fabric width and a little extra for mitred corners and diagonal joins. It returns the binding length, the number of strips to cut and the yardage.
The binding runs around the perimeter: perimeter = 2 × (width + length). Adding about 10 inches covers the corners and the seams where strips join, giving the total binding length. Strips = ceil(total ÷ fabric width), since each strip cut across the fabric yields roughly one fabric-width of binding. Fabric length = strips × strip width, and yardage = that ÷ 36, rounded up to the nearest eighth of a yard.
The 10-inch cushion keeps you from coming up short at the last corner; increase it if you like long tails for a neat join. Cut strips selvage-to-selvage for straight-grain binding, or on the bias for curved edges — bias needs a bit more fabric, which the companion bias-tape calculator handles.