Calculate molar mass from a chemical formula
A molar mass calculator adds the conventional atomic-weight contribution of every atom written in a chemical formula. Enter a formula such as H2O, C6H12O6, Ca(OH)2, or CuSO4·5H2O. The parser expands subscripts, nested parentheses, square brackets, leading hydrate coefficients, and hydrate dots before the mass is calculated, so the displayed element counts can be reviewed before the total is used.
The answer is reported in grams per mole, the mass of one mole of the stated formula units. Each result row shows the element symbol, expanded atom count, atomic weight, and subtotal. That breakdown makes the calculation useful for homework because it reveals whether an error came from the formula, a group multiplier, an omitted hydrate, or the final addition rather than presenting one unexplained number.
How the molar mass formula works
For each element, multiply its atom count by its conventional atomic weight, then add all element subtotals. Water therefore gives 2 × 1.0080 for hydrogen plus 1 × 15.999 for oxygen, or about 18.015 g/mol. Calcium hydroxide first expands (OH)2 to two oxygen and two hydrogen atoms before calcium, oxygen, and hydrogen contributions are added.
A coefficient after a hydrate dot belongs to that segment. CuSO4·5H2O contains one copper, one sulfur, nine oxygen, and ten hydrogen atoms. Forgetting to multiply the water segment produces the molar mass of anhydrous copper sulfate instead. The visible expanded counts provide a direct check that the formula was interpreted as the substance actually named in the question.
Enter formulas without changing their chemical meaning
Element symbols are case-sensitive: Co means cobalt, while CO represents carbon and oxygen. Use ordinary digits or Unicode subscripts, matching parentheses or brackets, and a middle dot or bullet for hydrates. A coefficient may follow a hydrate dot, but the compound formula itself must not start with a reaction coefficient. Empty groups, unknown symbols, zero subscripts, mismatched brackets, ambiguous bare charge magnitudes, and formulas longer than the stated limit are rejected with a specific correction.
Charges do not materially change the classroom molar mass obtained by summing atomic weights, but explicit charges should use a caret when a trailing digit would be ambiguous, such as Fe^3+ or SO4^2-. Electron mass is outside this formula-sum model. If a reagent name includes a solvate, hydrate, isotope label, or mixture, enter the exact chemical form intended by the problem rather than the shortest familiar formula.
Check units, scale, and significant figures
The numerical value of molar mass in g/mol often matches relative formula mass expressed in u or Da, but the quantities and units are not interchangeable. Molar mass describes a mole-sized sample; relative molecular or formula mass describes one molecular or formula unit on an atomic scale. Keep g/mol attached when the result is used to convert between mass and moles.
A quick scale check is useful. Compounds containing heavier atoms or more atoms per formula unit should normally have larger molar masses. Recalculate one subtotal independently and confirm that all subtotals add to the total. Retain the unrounded total during later stoichiometry and round only to the precision justified by the source masses, measurements, or course instructions.
Atomic-weight limits and private calculation
The calculator uses conventional abridged IUPAC atomic weights. Natural isotope composition can vary, radioactive elements may use a representative mass number, and a specifically enriched isotope requires its stated isotope mass instead. The page does not identify an unknown compound, infer a molecular formula from experimental data, or account for sample purity and measurement uncertainty.
The values are calculated in the current browser tab. NexaCurrent does not upload the quantities, formulas, chemical names, element choices, or other information entered here, and no account is needed. Copying is a deliberate action after the answer and working are visible. Refreshing or leaving the page clears the current calculation, so keep a copied result if it is needed for later study.