A full sew-in weave with Virgin Remy human hair, would need approximately 8 to 10 ounces of hair. We recommend buying 2 packs of hair for lengths 14” to 18”. We recommend 3 packs for lengths 20″or longer. Each bundles weighs 3. 5 ounces. Keep in mind that since the hair is sold by total weight the rule is: “The longer the hair, the shorter the weft.”