Orders of magnitude (mass)
Factor ( kg ) Value Item
10 8.9 × 10 kg Graviton
10 4.2 × 10 kg Mass equivalent of the energy of a photon at the peak of the spectrum of the cosmic microwave background radiation ( 0.235 meV/ c )
10 1.8 × 10 kg One eV/ c , the mass equivalent of one electronvolt
10 3.6 × 10 kg Electron neutrino , upper limit on mass ( 2 eV/ c )
10 9.11 × 10 kg Electron ( 511 keV/ c ) , the lightest elementary particle with a measured nonzero rest mass
10 3.0-5.5 × 10 kg Up quark ( as a current quark ) ( 1.7-3.1 MeV/ c )
10 1.9 × 10 kg Muon ( 106 MeV/ c )
10 yoctogram ( yg ) 1.661 × 10 kg Atomic mass unit ( u ) or dalton ( Da )
10 yoctogram ( yg ) 1.673 × 10 kg Proton ( 938.3 MeV/ c )
10 yoctogram ( yg ) 1.674 × 10 kg Hydrogen atom , the lightest atom
10 yoctogram ( yg ) 1.675 × 10 kg Neutron ( 939.6 MeV/ c )
10 1.2 × 10 kg Lithium atom ( 6.941 Da )
10 3.0 × 10 kg Water molecule ( 18.015 Da )
10 8.0 × 10 kg Titanium atom ( 47.867 Da )
10 1.1 × 10 kg Copper atom ( 63.546 Da )
10 1.6 × 10 kg Z boson ( 91.2 GeV/ c )
10 2.2 × 10 kg Higgs Boson ( 125 GeV/ c )
10 3.1 × 10 kg Top quark ( 173 GeV/ c ) , the heaviest known elementary particle
10 3.2 × 10 kg Caffeine molecule ( 194 Da )
10 3.5 × 10 kg Lead -208 atom
Units of mass -- Below 10−24 kg
Unlike other physical quantities , mass-energy does not have an a priori expected minimal quantity , as is the case with time or length , or an observed basic quantum as in the case of electric charge . Planck 's law allows for the existence of photons with arbitrarily low energies . Consequently , there can only ever be an experimental lower bound on the mass of a supposedly massless particle ; in the case of the photon , this confirmed lower bound is of the order of 3×10−27 eV = 10−62 kg .
To help compare different orders of magnitude, the following lists describe various mass levels between 10 kg and 10 kg.