A measurement of mass used for

elementary particles. The formula is 1

billion (G)

electron volts (eV) divided by (over)

the speed of light (c) squared. This measurement equals about 1.78 x 10^-36 kg (3.92 x 10^-36 lb). Following is a chart of some elementary particles and their mass:

Up Quark: .0015 to .005
Down Quark: .003 to .009
Strange Quark: 1.1 to 1.4
Charm Quark: .06 to .17
Top (truth) Quark: about 170
Bottom (beauty) Quark: 4.1 to 4.4
Photon: 0?
Gluon: 0?
W+: 80
W-: 80
Z: 91
Proton: .938
Neutron: .940
Sigma+: 1.189
Sigma-: 1.193
Lamda+-: 1.116
Pion+: .14
Pion+-: .135
Pion-: .14
Kaon+: .494
Kaon-: .494
D+: 1.869
D-: 1.869

Thanks to Chen Ning Yang for the table.