Atomic mass units (u) to Grams Converter

About this calculator

The atomic mass unit (u), also called the dalton, is defined as exactly 1/12 the mass of a neutral carbon-12 atom, equal to 1 u = 1.66053906892×10⁻²⁴ grams — a figure fixed by the relationship u = 1/(NA × 1000), where NA is Avogadro's number, since one mole of a substance with molar mass M grams contains NA atoms/molecules each of mass M/NA grams.

Chemists and physicists work in atomic mass units when quoting atomic and molecular masses (an oxygen atom is about 16 u) because the numbers stay conveniently small, then convert to grams or kilograms whenever a calculation needs to interface with macroscopic, SI-based quantities like reaction yields or mass spectrometry calibration.