To measure the length of the Grand Piano, measure in a straight line from very front of the keyboard to the very rear of the piano. You will need to measure the full length of your piano, so be sure to measure from the very back end to the very front of the keyboard. Once you have the measurement you will now use it to select the cover that fits your Grand Piano or Baby Grand Piano. Example: If your Grand Piano measures 5′ 1″, you will choose the cover that fits a 5’0″ to 5’2″ Grand Piano. It is that easy.