# What makes neutron heavier than a proton? [duplicate]

The mass of proton is 1.672 × 10−27 kg while it is 1.675 × 10−27 kg. Both are made up of 3 quarks each. Then what makes proton lighter than a neutron?

• This question does not have an answer. The "answers" to the duplicate are non-answers. – John Duffield Aug 14 '15 at 13:13

Note that the combined rest masses of the quarks (~10 MeV/$c^2$) account for about 1% of the proton and neutron mass (~938 MeV/$c^2$), the main contribution to the mass are the gluons from the Strong Force. Since the composition of the proton and neutron are different, so is the force that binds them.