What is the mass of a proton?

The mass of a proton is approximately 1.007276 amu (atomic mass units) or 1.6726219 x 10^-27 kg. It is one of the three subatomic particles found in the nucleus of an atom, along with neutrons and electrons. The mass of a proton is slightly less than the mass of a neutron, which is approximately 1.008665 amu or 1.674927 x 10^-27 kg. Protons have a positive charge and are essential to the structure and stability of an atom. They determine the atomic number of an element, which is the number of protons in the nucleus.