An angstrom (Å) is a unit of measurement often used in chemistry, most often in reference to molecules; for example, the average molecule diameter is between 0.5 to 2.5 angstroms. An angstrom is equal to about 3.937 × 10^-9 inch or one hundredth of a millionth of a centimeter (10^-8 centimeter). (For more information about measurement, see “Mathematics throughout History.”)