Molecular Mass Calculator

How to calculate the mass of a
particular isotopic composition

Enter the molecular formula of the molecule.
Examples: C6H12O6, PO4H2(CH2)12CH3

Standard Masses

Standard Formula Weight:   15.999400

Mono-isotopic molecular masses:
12C/14N:    18.0105646863
13C/14N:    18.0105646863
12C/15N:    18.0105646863
13C/15N:    18.0105646863

Calculate molecular mass by:

Molecular Mass for H2O = 18.015286 Da

Charge = 0

1H    1.007825
2H (D)   2.014102
3H (T)   3.016049

Average mass of this isotopic composition of H: 1.007941 Da

16O    15.994915
17O    16.999132
18O    17.999160

Average mass of this isotopic composition of O: 15.999405 Da

Masses and Isotopic Compositions came from the NIST Physical Reference Data
*This mass was calculated from the distribution displayed in the text inputs.