Look at the information you receive. You can find the atomic mass of an element from the abbreviated form or its name.
Consider the numeric portion of an element's name. Plutonium-244, for example, tells its atomic mass -- 244 -- in the number incorporated in its name.
Look for a number to the right of the element's abbreviation. Standard abbreviations begin with the atomic number as a subscript followed by the abbreviated element name and then the atomic mass as a superscript notation. Plutonium 244 would be 94PU 244 or PU244. The number to the right of the element abbreviation is always the atomic mass.
Find the atomic weight of an atom. Round the atomic weight number up to the nearest whole number to get the atomic mass. The atomic mass is the number of electrons, neutrons and protons in the atom, while the atomic weight is an average measure of all the common isotopes of the element, according to the Jefferson Lab.