It depends upon the weight of the item you are dyeing. As a general guideline, one box of powder dye or 4 ounces of liquid dye will color one pound of dry weight fabric (about 3 yards of lightweight fabric or two adult large t-shirts). To obtain a lighter color, use less dye. For a darker or brighter color, double the amount of dye. We recommend at least 1 bottle of Rit All-Purpose Dye or 2 bottles of Rit DyeMore for darker colors. If dyeing 100% polyester, we recommend at least 1 bottle of Rit DyeMore.
You can estimate the weight of the item or use a food or home postal scale. For larger items, such as bedding or curtains, weigh yourself; then weigh yourself holding the item(s). The difference is the weight of the item(s).