Today, the most common standard sizes that are easily available are:
2x3, 3x5, 4x6, 6x9, 8x10, 9x12, 10x14, 12x15, 12x18.
The square rugs measure 3x3, 4x4, 5x5 6x6, 7x7, 8x8, 10x10, 12x12, 14x14 and larger. These are usually available, too.
Rounded ones similar to square types have these dimensions: 2.5x 6, 2.5x8, 2.3x10, 2.5x12, 2.5x14.up to 2.5x36.