Chemical Weight Calculator

Element symbols with counts. Groups may be nested with ( ), [ ] or { }. Hydrates use a dot: CuSO4*5H2O. Ions may carry a trailing charge: SO4^2-.
Used by the mass-to-moles mode.
Used by the moles-to-mass mode.
Molar mass
18.0150 g/mol
Molar Mass Calculator
Monoisotopic (exact) mass
18.010565 Da
Formula as parsed
H2O
Atoms per formula unit
3
Net ionic charge
0
Worked out from IUPAC Commission on Isotopic Abundances and Atomic Weights - Standard Atomic Weights (abridged, five significant figures) and 3 other sources.
Masses use the IUPAC/CIAAW abridged standard atomic weights. Check the parsed formula shown in the result before using these figures for reagent preparation, dosing or regulatory reporting.

How this is worked out

4 steps
  1. Parsed formula: H2O
  2. H: 2 x 1.008 = 2.016 g/mol (11.1907 % by mass)
  3. O: 1 x 15.999 = 15.999 g/mol (88.8093 % by mass)
  4. Molar mass = 18.015 g/mol
Percent composition by masstable
symbolelementatomsatomicWeightmassContributionpercentByMass
HHydrogen21.0082.01611.190674
OOxygen115.99915.99988.809326

Results are general information, not financial, tax, legal, medical or engineering advice.