Give each edge enough overhang
Start with the measured quilt-top size. Enter the extra batting you need on the left, right, top and bottom. These amounts can differ, which is useful when your quilting setup needs more room at one end. Check the requirements of your quilting method or longarm quilter before settling on the allowances.
Check the rectangle against your roll
A 60 × 80-inch quilt top with 4 inches added on every edge needs a 68 × 88-inch piece of batting. If you're buying a packaged size, compare both dimensions with that rectangle. If you're cutting from a roll, enter the roll width. Leave it at zero when you only need the finished batting rectangle.
Turn the batting only when it fits
If the rectangle is too wide for the roll, you can allow rotation to check the other direction. The calculator reports a roll length only when one permitted orientation fits. It doesn't plan batting joins. The roll length is an exact cutting length, so check how the seller rounds purchases before ordering.