However, the one aspect of fit you may want to consider is pocket depth. Fitted sheets can vary in how deep the pockets are, since mattress heights are not standardized like length and width. If your mattress is more than 10 inches tall, you may want to consider looking specifically for deep-pocket fitted sheets. We recommend the pockets be a few inches larger than the height of your bed — if your bed is 15 inches tall, look for 16 to 17 inch pockets.