Molecular Weight Conversion Calculator
Convert molecular weight between Daltons (Da), atomic mass units (amu), grams per mole (g/mol), and kiloDaltons (kDa). Enter a chemical formula to calculate the molecular weight, then use the value in any unit system. Understand the relationship between Da, amu, g/mol, and kDa — and when to use each in chemistry, biochemistry, and mass spectrometry.
Ingrese una fórmula química arriba para calcular el peso molecular
Molecular Weight in All Units
Calculate once, express in any molecular weight unit.
Molecular weight units can be confusing because three common units — g/mol, Da, and amu — are all numerically identical. A water molecule has a molecular weight of 18.015 g/mol = 18.015 Da = 18.015 amu. The only conversion needed is to kDa: divide by 1000.
The choice of unit depends on your field: organic chemists use g/mol, biochemists use kDa for proteins, mass spectrometrists use Da and m/z ratios, and physicists use amu. This calculator gives results in g/mol, which can be used interchangeably with Da and amu.
For the absolute mass of a single molecule in grams, multiply the Da value by 1.66054 × 10⁻²⁴ g. But for all practical chemistry, the g/mol value is what you need.
Atomic Weights in Da / amu / g/mol
Each element's atomic weight can be expressed in any of these equivalent units.
Every atomic weight can be expressed in Da, amu, or g/mol — the values are identical. Carbon weighs 12.011 Da = 12.011 amu = 12.011 g/mol. The Dalton is named after John Dalton, who first proposed the atomic theory.
For biochemistry and proteomics, kiloDaltons (kDa) are practical: hemoglobin is ~64.5 kDa rather than 64,500 Da. Antibodies are typically ~150 kDa, and ribosomes reach ~2,500 kDa.
Explore element atomic weights below — each value works in Da, amu, and g/mol simultaneously.
How to Convert Molecular Weight Units
Calculate the molecular weight, then express it in any unit.
Enter a Chemical Formula
Type any formula from simple molecules to large biomolecules. The calculator computes the molecular weight in g/mol — the base unit from which all other molecular weight units can be derived. Results can be mentally converted: g/mol = Da = amu (all numerically equal).
Molecular Weight in Multiple Units
Click any compound to see its molecular weight expressed in all units.
Molecular Weight Conversion FAQ
Questions about Da, amu, g/mol, kDa, and unit conversions.