pattiann42
Fleece comes in 54 - 60 inch widths. You cut away and do not use the selvage edges (long edge that is thick and may have needle holes from the manufacturing process). This will leave you with about 2" less in width. 1 1/2 yards will be be 54" long. 1 3/4 yards will be 63" Choose the yardage based on the width of the fleece (this will be printed on the cardboard center of the material) for symmetry. If the adult is 6' or over, then 2 yards (72") or more might be considered for the length.

Webwise
You have to consider the bulkiness of fleece for washing. Anything more than 2 yards is a tight fit in the washer. If it's just a throw size that you want to make, then no more than 1 1/2 yards, as the person's height is insignificant. A typical throw is usually 42-46", so the 1 1/2 yards works out to 54" which is a good size to wrap around your recipient. If you are fringing the edge all the way around, this will take another 6" off your total length and width as usable blanket.