What size is a single flat sheet? Rebecca L October 26, 2020 18:28 Updated Follow Our single flat sheets measure 178cm x 254cm. Shop single flat sheets. Related articles What size is a single fitted sheet? What materials are used to make our Poly Cotton bed linen and what are their benefits? What size is a double flat sheet? What size is a double duvet cover? What is thread count? (TC) Comments 0 comments Please sign in to leave a comment.