Need to know what size Sofa Cover you need? Our sofa covers come in 4 sizes. Small, Medium, Large and X-Large. measure your sofa from arm to arm as shown in the drawings below, be sure to include the drop from the arm to the seat cushion. Once you have your measurement just match it up with the right cover. All Pillowcases are 45x45cm. Please note that L-shaped and U-shaped sofa’s will require more than one cover.