Flat bed sheets, also known as top sheets, are longer and wider than the fitted sheets that cover the mattress. Flat sheets are long enough to tuck under the mattress at the end of the bed and cover the pillow at the head of the bed. There are flat sheets for twin, full, queen and king size beds.
Twin mattresses come in two different sizes. The twin size bed is 39 inches-by-75 inches while the twin extra long is 39 inches-by-80 inches. The flat sheet size for a twin bed is 66 inches-by-96 inches. Flat sheets for the twin extra long mattress are 70 inches-by-102 inches. Flat sheets for the twin or twin extra long can be purchased separately or in a set with a fitted sheet and one standard pillow case.
The full size mattress, also known as a double bed mattress, is 54 inches-by-75 inches. Flat sheet sizes for the full mattress are 80 inches-by-94 inches. Flat sheets for the full size mattress can be purchased in a set with a fitted sheet and two standard pillow cases, or separately.
Queen size mattresses are 60 inches-by-80 inches. Queen size flat sheets measure 90 inches-by-102 inches. Queen size flat sheets are sold separately or in sets with a fitted sheet and two standard pillow cases.
The king size mattress, also known as the Eastern king, is 76 inches-by-80 inches while the California king mattress, also known as the Western king, is 72 inches-by-84 inches. Flat sheets for a king size mattress are 110 inches-by-102 inches. California king flat sheets are 108 inches-by-102 inches. These flat sheets come in sets with a fitted sheet and two king size pillow cases, or separately.