The weight of atoms and molecules are measured in Unified Atomic Mass Units (u) or in grams per mole (g/mol). The mass in an atom depends almost entirely on the number of protons and neutrons in the atom. You can convert u into other mass units like grams by multiplying by Avagadro's number which is 6.022*10^23.

This calculator computes the total molar mass and mass percent of any element or compound. You can choose from common compounds and atoms in the drop down menus or experiment by typing your own!