Protons have a mass of approximately 1 atomic mass unit (amu), neutrons have a mass of approximately 1 amu, electrons have a mass of approximately 1/1836 amu, and quarks have masses that vary depending on the type of quark. For example, the up quark has a mass of approximately 2 MeV/c2, the down quark has a mass of approximately 5 MeV/c2, and the charm quark has a mass of approximately 1.3 GeV/c2.