Tech-Info 02: What the fill factor number means

The fill factor of a strand is defined as the ratio of the metallic cross section (or as simplified calculation the sum of the single wire cross sections) related to the area of the smallest circle enclosing the strand. The fill factor specifies the amount of space which the strand takes in the rope meaning the quantity of steel. The fill factors of the most common strands are between 0,70 and 0,82. This means, that the amount of steel in the strand is about 70% to 82%. The fill factors of strands can be considerably increased by compacting. Usually the fill factor of a strand increases with an increasing number of wires. A Seale 15 strand (1-7-7) for example has a fill factor of about 0,77 and a Seale 19 strand (1-9-9) has a fill factor of about 0,79.