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Molecular Weight Calculator

Molecular Weight Calculator

This online calculator you can use for computing the average molecular weight (MW) of molecules by entering the chemical formulas (for example C3H4OH(COOH)3 ). Or you can choose by one of the next two option-lists, which contains a series of common organic compounds (including their chemical formula) and all the elements. The molecular mass calculator will recognize the entered formula's, which are included in the list of organic compounds.
The calculator handles at most two different bracket levels. Make sure you enter the molecule of crystallization at last (e.g. C2HCl3O.H2O ).

Common Organic Compounds

Elements of the periodic table


Chemical formula:

# Atom Molar Mass (MM) Subtotal Mass Subtotal Mass
(g/mol) (%) (g/mol)

Total Molecular Weight:

!!! Lenntech BV cannot be held responsible for errors in the calculation, 
the program itself or the explanation. For question or remarks please contact us.
This Calculator has been tested on Internet Explorer version 6 only,
Firefox might not show all fields correctly.


Molecular mass or molar mass are used in stoichiometry calculations in chemistry.
In related terms, another unit of mass often used is Dalton (Da) or unified atomic mass unit (u) when describing atomic masses and molecular masses. It is defined to be 1/12 of the mass of one atom of carbon-12 and in older works is also abbreviated as "amu".

Also, important in this field is Avogadro's number (NA) or Avogadro's constant (6.0221 x 1023).
The term "mole" is defined in that one mole of a substance with a molecular (or atomic) mass of one (1), will have a mass of 1 gram. Or 1 mole of a substance will contain Avogadro's number of that substance. Using the above calculator you could find that e.g. a pollution of 1 gram of benzene in a certain amount of water converts to NA/78.11≈ 7.7098 × 1021 molecules polluting that water!

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