The atomic mass unit (amu) is defined as 1/12th the mass of a carbon-12 atom. While protons and neutrons have slightly different masses, they are both approximately 1 amu.

Here's a more precise breakdown:

* Proton: 1.007276466879 amu

* Neutron: 1.00866491588 amu

As you can see, they are very close to 1 amu, which is why it's a convenient approximation for calculations.