Abstract: In the prior art it is known to determine the density of a roll of paper as it is being wound on a paper receiving roll. The determination is made each time the paper receiving roll makes a constant predetermined number of revolutions. Because the diameter of the paper on the paper receiving roll increases, there is an increasing length of paper added between successive determinations. This makes it more difficult to maintain a desired roll density by controlling various factors during winding. In addition, because the paper web is usually fed onto the roll at a constant rate, the time between successive density determinations increases. The system of the invention provides for an adjustment of the predetermined number of revolutions between density determinations. This number is decremented to provide, very approximately, the same time interval between successive determinations.