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    Molar Mass Calculator

    The molar mass of a substance from its chemical formula: the atoms of each element, their contributions and mass fractions, by IUPAC standard atomic weights

    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

    Molar Mass

    Molar mass is the mass of one mole of a substance: the sum of the atomic weights of all the atoms in its formula, in g/mol.

    Example: H2SO4

    M(H2SO4) ≈ 98.07 g/mol

    Contribution of each element
    Element Atoms, n Atomic weight, A n × A, g/mol Mass fraction, w
    Hhydrogen21.00802.0160 w ≈ 2.06%
    Ssulfur132.0632.06 w ≈ 32.69%
    Ooxygen415.99963.996 w ≈ 65.25%
    Σ = 98.072 ≈ 98.07 g/mol w = 100%

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

    Mass fractions of the elements

    S 32.69%H 2.06%

    Molar masses of the elements, g/mol (CIAAW 2024)
    ZElementM, g/mol
    1H — hydrogen1.0080
    2He — helium4.0026
    3Li — lithium6.94
    4Be — beryllium9.0122
    5B — boron10.81
    6C — carbon12.011
    7N — nitrogen14.007
    8O — oxygen15.999
    9F — fluorine18.998
    10Ne — neon20.180
    11Na — sodium22.990
    12Mg — magnesium24.305
    13Al — aluminium26.982
    14Si — silicon28.085
    15P — phosphorus30.974
    16S — sulfur32.06
    17Cl — chlorine35.45
    18Ar — argon39.95
    19K — potassium39.098
    20Ca — calcium40.078
    21Sc — scandium44.956
    22Ti — titanium47.867
    23V — vanadium50.942
    24Cr — chromium51.996
    25Mn — manganese54.938
    26Fe — iron55.845
    27Co — cobalt58.933
    28Ni — nickel58.693
    29Cu — copper63.546
    30Zn — zinc65.38
    31Ga — gallium69.723
    32Ge — germanium72.630
    33As — arsenic74.922
    34Se — selenium78.971
    35Br — bromine79.904
    36Kr — krypton83.798
    37Rb — rubidium85.468
    38Sr — strontium87.62
    39Y — yttrium88.906
    40Zr — zirconium91.222
    41Nb — niobium92.906
    42Mo — molybdenum95.95
    44Ru — ruthenium101.07
    45Rh — rhodium102.91
    46Pd — palladium106.42
    47Ag — silver107.87
    48Cd — cadmium112.41
    49In — indium114.82
    50Sn — tin118.71
    51Sb — antimony121.76
    52Te — tellurium127.60
    53I — iodine126.90
    54Xe — xenon131.29
    55Cs — caesium132.91
    56Ba — barium137.33
    57La — lanthanum138.91
    58Ce — cerium140.12
    59Pr — praseodymium140.91
    60Nd — neodymium144.24
    62Sm — samarium150.36
    63Eu — europium151.96
    64Gd — gadolinium157.25
    65Tb — terbium158.93
    66Dy — dysprosium162.50
    67Ho — holmium164.93
    68Er — erbium167.26
    69Tm — thulium168.93
    70Yb — ytterbium173.05
    71Lu — lutetium174.97
    72Hf — hafnium178.49
    73Ta — tantalum180.95
    74W — tungsten183.84
    75Re — rhenium186.21
    76Os — osmium190.23
    77Ir — iridium192.22
    78Pt — platinum195.08
    79Au — gold196.97
    80Hg — mercury200.59
    81Tl — thallium204.38
    82Pb — lead207.2
    83Bi — bismuth208.98
    90Th — thorium232.04
    91Pa — protactinium231.04
    92U — uranium238.03
    Molar masses of common substances
    SubstanceM, g/mol
    H₂O (water)18.015
    NaCl (sodium chloride)58.44
    CO₂ (carbon dioxide)44.009
    H₂SO₄ (sulfuric acid)98.07
    NaOH (sodium hydroxide)39.997
    CH₄ (methane)16.043
    C₆H₁₂O₆ (glucose)180.156
    C₁₂H₂₂O₁₁ (sucrose)342.297

    Common mistakes

    • CO and Co are different substances: M(CO) = 28.010 g/mol (carbon monoxide), M(Co) = 58.933 g/mol (cobalt). Write each symbol with a capital letter: a lowercase letter continues the symbol before it.
    • An oxygen atom and oxygen gas are not the same: M(O) = 15.999 g/mol, while the gas is made of molecules, M(O₂) = 31.998 g/mol. In a gas problem, «the molar mass of oxygen» usually means O₂.
    • Chemistry uses g/mol, SI and physics use kg/mol: M(H₂SO₄) ≈ 98.07 g/mol = 0.09807 kg/mol. Mixing them makes the answer 1,000 times off.
    • The water of a crystal hydrate counts: M(CuSO₄·5H₂O) ≈ 249.68 g/mol, while without the water M(CuSO₄) ≈ 159.60 g/mol.

    See Also

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    FAQ

    How to find the molar mass from a chemical formula?

    Multiply the atomic weight of each element by the number of its atoms and add everything up. For H₂SO₄: 2 × 1.0080 + 32.06 + 4 × 15.999 = 98.072 ≈ 98.07 g/mol. Brackets multiply everything inside them, and the water of a hydrate counts too.

    What is the difference between molar mass and molecular mass?

    The number is the same, the meaning differs: the molecular mass of H₂SO₄ is 98.07 u (daltons) — the mass of one molecule; the molar mass is 98.07 g/mol — the mass of one mole, 6.022 × 10²³ molecules.

    Why do school problems use round numbers?

    Textbooks round atomic weights to whole numbers (chlorine to 35.5) so the sums are easy to do by hand: H₂SO₄ gives 2·1 + 32 + 4·16 = 98 g/mol. The IUPAC table gives 2 × 1.0080 + 32.06 + 4 × 15.999 = 98.072 ≈ 98.07 g/mol; for lab work, use the table values.

    How to convert grams to moles?

    Divide the mass by the molar mass: n = m / M. For example, 49.035 g of H₂SO₄ is 49.035 ÷ 98.07 = 0.5 mol. Back: m = n × M.