The atomic mass of a proton is approximately 1.007276 atomic mass units (u) or 1.67262192 × 10^(-27) kilograms. The atomic mass unit (u) is a unit of mass used to express atomic and molecular weights on a relative scale, where 1 atomic mass unit is defined as 1/12th the mass of a carbon-12 atom. The value of the proton's atomic mass is very close to 1 atomic mass unit, but it is slightly greater due to the contributions of the proton's binding energy.