How to calculate molar mass
Enter a chemical formula, choose a result unit, and click Calculate. The calculator parses the formula, applies standard atomic weights, and shows the formula, total molar mass, calculation steps, and an element-by-element breakdown.
How the calculation works
For each element, the calculator multiplies its atom count by its standard atomic weight in g/mol, then adds those contributions:
Molar mass = sum of (atom count x standard atomic weight)
Breakdown contribution values remain in g/mol, even when the selected result unit is kg/mol or mg/mmol.
Supported formulas and limitations
Use case-sensitive element symbols, such as Co for cobalt. The parser supports integer subscripts, nested parentheses and brackets such as Ca(OH)2 and Al2(SO4)3, and hydrates with a dot or asterisk before the water count, such as CuSO4.5H2O or CuSO4*5H2O.
- The formula field is required.
- Unknown symbols, unbalanced parentheses or brackets, and unsupported characters produce errors.
- Enter a formula yourself. Names, trade names, and CAS numbers are not identified.
- The calculator uses standard atomic weights for naturally occurring element mixtures and does not resolve isotope-specific masses.
Choose the result unit
Use the Result unit control to choose g/mol, kg/mol, or mg/mmol. The calculation uses g/mol as its basis; kg/mol is the g/mol result divided by 1000, while mg/mmol is numerically identical to g/mol.
How to use the Molar Mass Calculator
- Enter a formula in the Chemical formula field, or click an example formula button. An example fills the field and calculates immediately.
- Choose an option under Result unit.
- Click Calculate to display the result and breakdown.
- Click Reset to clear the formula, return the unit to g/mol, and hide the result.
If the formula is invalid, the previous result is hidden and an error message is shown.
Copy or download the result
- Download result (.txt) creates a plain-text file.
- Copy result uses the browser Clipboard API. If clipboard access fails, the interface reports that you should select and copy manually. The current result output is hidden, so a usable manual-copy fallback is not confirmed.
Privacy and calculation scope
The calculation runs locally in your browser using the script's atomic-weight table, and the calculator script does not upload the formula you enter. The page also loads analytics, records page-view/tool-hit data, and includes a server-backed subscription form.
Frequently Asked Questions
How is molar mass calculated from a chemical formula?
Molar mass is the sum, over every element in the formula, of that element's atom count multiplied by its standard atomic weight in g/mol. For example, H2O has 2 hydrogen atoms (1.008 g/mol each) and 1 oxygen atom (15.999 g/mol), giving 2.016 + 15.999 = 18.015 g/mol.
What chemical formulas can this calculator read?
It reads standard element symbols with integer subscripts, nested parentheses or brackets such as Ca(OH)2 or Al2(SO4)3, and hydrates written with a dot or asterisk before the water count, such as CuSO4.5H2O. Unknown symbols, unbalanced parentheses or brackets, and unsupported characters produce errors. It uses standard atomic weights for naturally occurring element mixtures; it does not identify an unknown compound from a name or resolve isotope-specific masses.
What units does this calculator support?
Results can be shown in g/mol, kg/mol, or mg/mmol. The mg/mmol value is numerically identical to g/mol, and g/mol is the calculation basis.
Does this tool identify an unknown chemical for me?
No. You must supply a valid chemical formula yourself. This tool does not identify a compound from a common name, trade name, or CAS number, and it does not provide laboratory safety guidance.