Molar mass

Formula

Choose an example or enter a composition, then calculate. Element symbols are case-sensitive: Co is cobalt; CO is carbon monoxide. Normal digits and subscripts are accepted. Nested (), [] and {} groups work, as do hydrates such as CuSO4·5H2O. A period is also a hydrate separator; fractional counts, charges and isotope notation are not supported. Each dot component has its own coefficient: CuSO4·5H2O·2NH3 adds five waters and two ammonias. A leading coefficient multiplies the entire composition, including all hydrates.

Results and precision

The total is the sum of atom count × tabulated atomic weight, in g/mol. For 2H2O it is the mass of two formula units per mole of the specified composition, not the unchanged molar mass of water. The table shows count, mass contribution and percentage for each element. Atomic weights and localized names are available in the details. Hill order places C and H first when carbon is present; otherwise symbols are alphabetical. Unrounded values determine the percentages; displayed rounding need not sum to exactly 100%.

The bundled element data use rounded conventional weights and representative isotopes where no standard weight exists. Natural isotope abundances affect actual masses. This is not an exact-isotope mass calculator or a structure validator. At most 512 characters, 16 nested group levels and exactly representable positive integer counts are accepted.

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Reference: CIAAW standard atomic weights.