Molar Mass of H2O (Water)

Molar Mass Calculator
Chemical formula Write symbols with a capital letter: CoCl2 is cobalt chloride, COCl2 is phosgene. A hydrate takes a dot: CuSO4·5H2O or CuSO4.5H2O

What is the molar mass of H2O?

Answer

M(H2O) =
18.015 g/mol

Atomic weights: IUPAC standard values (CIAAW, 2024).

Contribution of each element
Element Atoms, n Atomic weight, A n × A, g/mol Mass fraction, w
Hhydrogen21.00802.0160 w ≈ 11.19%
Ooxygen115.99915.999 w ≈ 88.81%
Σ = 18.015 g/mol w = 100%

Atomic weights: CIAAW, Abridged Standard Atomic Weights (2024)

Mass fractions of the elements

H 11.19%

Related Calculations

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Recalculate with different values ↑

Molar masses of substances nearby

FormulaM, g/mol
O (oxygen)15.999
CH₄ (methane)16.043
NH₃ (ammonia)17.031
H₂O (water)18.015
F (fluorine)18.998
HF (hydrogen fluoride)20.006
Ne (neon)20.180

FAQ

What is the molar mass of H2O?

M(H₂O) = 18.015 g/mol

How to calculate the molar mass of H₂O?

Add up the atomic weights of all the atoms in the formula: 2 × 1.0080 + 15.999 = 18.015 g/mol.

How many grams are in 2 moles of H₂O?

m = n × M = 2 mol × 18.015 g/mol = 36.030 g.

See Also