The molar mass of potassium iodide, written with the formula KI, is about 166.0028 grams per mole. As with all chemicals, the molar mass of potassium iodide is determined by adding together the mass of all the atoms in it.
The molar mass of potassium iodide is the sum of the mass of one atom of potassium, which is about 39.0983 grams per mole, and the mass of one atom of iodine, which is about 126.904 grams per mole. Those masses are derived from the atomic weight of each element, which is listed on the periodic table of elements. Potassium iodide is often used as a nutritional supplement.