Define atomic mass unit: One atomic mass unit (u)

One atomic mass unit (u) is defined as the 1/12 th of the mass of the isotope of carbon 𝐴 1 2 6 𝐴 2 1 2 2 6 C. The SI unit of atomic ... An atomic mass unit is used to measure atomic and molecular masses based on carbon-12. Unified atomic mass unit, or u, is the preferred term in the SI measurement system. One AMU is equal to 1 u or 1 Da, and was redefined based on carbon-12 in 1961. Learn what 1 atomic mass unit (AMU) is equal to in different units of mass, such as kilograms, grams, electron volts, and daltons. Find out why AMU is important in chemistry and physics and how it is used to calculate molecular masses.