Plasmid MapCalculate molar mass from a formula
Molar mass is the mass of one mole of a substance, expressed here in grams per mole. This calculator reads the element symbols and their counts, multiplies each count by its atomic-weight value, and adds the contributions. The table makes those steps visible and reports each element's percentage of the calculated mass.
Enter a formula such as C6H12O6, Ca(OH)2 or CuSO4·5H2O. Capitalization matters: Co is cobalt, while CO contains carbon and oxygen. Parentheses and square brackets can group atoms, and a number after a group multiplies everything inside it. Unicode subscripts such as H₂O are accepted and normalized to ordinary digits.
Worked example: copper sulfate pentahydrate
For CuSO4·5H2O, the anhydrous part contributes one copper, one sulfur and four oxygen atoms. The hydrate contributes ten hydrogen and five additional oxygen atoms. The complete count is therefore Cu₁S₁O₉H₁₀.
Using this table's point values, the contributions are 63.546 from copper, 32.06 from sulfur, 143.991 from oxygen and 10.080 from hydrogen, giving 249.677 g/mol, displayed as 249.68 g/mol. The matching example is loaded above. Removing the water changes the result to 159.60 g/mol at display precision; a hydrate's waters belong in the formula used for preparing a solution.
Use the middle dot · between hydrate parts. An ordinary period is rejected because it can be confused with a decimal atom count. Leading coefficients are accepted after a hydrate separator, such as the 5 in ·5H2O. Fractional counts, leading isotope numbers and ionic charge notation are not supported.
Which atomic weights are used?
The calculator uses the 2024 abridged standard atomic weights published by the Commission on Isotopic Abundances and Atomic Weights. The pinned table supplies numerical values for 84 elements. An element without a standard atomic weight produces an explanation rather than a substituted isotope mass number.
The visible breakdown includes each source value and its stated uncertainty. Calculations use the point values; the uncertainties are not propagated into a final error estimate. Natural isotopic variation and enriched materials can require different values. This tool does not calculate monoisotopic or isotope-specific mass, identify a compound from its name, or verify that a formula corresponds to a real compound.
From molar mass to a solution
Molar mass and molarity describe different quantities: grams per mole versus moles per liter. The molarity calculator accepts the same chemical formulas, so you can calculate solute mass, concentration or final volume without retyping a rounded molecular-weight value. Use the dilution calculator when starting from an existing stock solution.
Copy calculation or Save calculation keeps the formula, method and breakdown together. Table CSV exports the displayed composition rows for a spreadsheet. All calculations and downloads stay in your browser. A molecular formula is not a purity measurement or a preparation protocol.