Do protons weigh the same as neutrons? YES AND NO When using Relative Atomic Mass (Mr), a proton weighs the same as a neutron. This is rounded to the nearest whole number, however. The actual weight of … a proton is 1.0073 amu. The actual weight of a neutron is 1.0087 amu. As you can see the neutron actually has slightly more mass (weight) than a proton has. When using figures to calculate Mr, however, as in most periodic tables, the mass of protons and neutrons is both 1.