A Fat Quarter is approximately 18" x 21", and is one quarter yard of fabric. It is cut by cutting one half yard of fabric off the bolt and then cutting that in half along the fold. Generally speaking, it is a more versatile size of fabric for a quilter.

Fat Quarter bundles are an excellent way to get lots of varieties of fabrics without having to buy such a large quantity. Fat quarters are sold in bundles containing one fabric from each of a fabric line, or they are bundles created around a color theme.