Molar Mass Calculator
Type a chemical formula โ for example C6H12O6 or Ca(OH)2 โ to calculate its molar mass in grams per mole.
Molar mass is the mass of one mole of a substance in grams per mole, found by adding up the atomic weights of every atom in its formula. Glucose (CโHโโOโ) has a molar mass of 180.16 g/mol: six carbons (72.07), twelve hydrogens (12.10) and six oxygens (96.00). It numerically equals the substance's molecular weight in atomic mass units.
How to Use This Calculator
Type a chemical formula into the box. Use a capital letter for the first letter of each element and a lowercase letter for the second, exactly as on the periodic table โ Na for sodium, Cl for chlorine, Ca for calcium. Put the number of atoms after each element as a subscript typed on the line: water is H2O, glucose is C6H12O6. For groups that repeat, use parentheses or brackets with a multiplier, such as Ca(OH)2 or (NH4)2SO4.
The calculator instantly returns the molar mass in grams per mole, along with a breakdown showing each element's contribution. If you type an unknown symbol or unbalanced parentheses, it will tell you what went wrong.
How the Calculation Works
Molar mass is the sum of the standard atomic weights of all the atoms in one formula unit. The tool parses your formula into its elements and their counts, multiplies each element's count by its atomic weight (in g/mol), and adds the results. Parentheses multiply everything inside them by the following subscript before adding to the total. The atomic weights are the IUPAC conventional standard values โ for example H = 1.008, C = 12.011, O = 15.999 g/mol.
Worked Example
Take glucose, CโHโโOโ. Carbon: 6 ร 12.011 = 72.066. Hydrogen: 12 ร 1.008 = 12.096. Oxygen: 6 ร 15.999 = 95.994. Add them: 72.066 + 12.096 + 95.994 = 180.156 g/mol. For a formula with parentheses like Ca(OH)โ: calcium 1 ร 40.078, oxygen 2 ร 15.999 = 31.998, hydrogen 2 ร 1.008 = 2.016, totaling 74.092 g/mol.
What the Result Means
Molar mass is the bridge between the mass you can weigh on a balance and the number of moles you need for a reaction. Grams divided by molar mass gives moles; moles times molar mass gives grams. It numerically equals the molecular weight (in atomic mass units) of a single molecule. Chemists use it constantly โ to prepare solutions of a known molarity, to find limiting reactants, and to convert reaction quantities between mass and moles.
Assumptions and Limitations
The calculator uses standard atomic weights, which are averages over the natural isotopic abundances of each element โ so results reflect a normal terrestrial isotopic mix, not a specific isotope. It covers the common elements and reads formulas with nested parentheses and brackets, but it does not interpret hydrate dot notation (write out the atoms instead), charges, or state symbols. Type element symbols with correct capitalization; 'co' is not recognized, while 'Co' is cobalt and 'CO' is carbon monoxide.
When to Use a Molar Mass Calculator
Chemistry students and lab technicians use this to get a compound's molar mass in grams per mole straight from its formula. Run it for stoichiometry, to convert between grams and moles, or when preparing solutions. Type a formula, including parentheses, to get the molar mass and a per-element breakdown.
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Frequently Asked Questions
What is molar mass?
Molar mass is the mass of one mole of a substance, in grams per mole. It equals the sum of the atomic weights of all atoms in the chemical formula and numerically matches the molecular weight.
How do I calculate molar mass by hand?
Multiply each element's atomic weight by the number of those atoms in the formula, then add all the products. For water, H2O: 2 ร 1.008 + 15.999 = 18.015 g/mol.
Is molar mass the same as molecular weight?
They are numerically equal. Molecular weight is the mass of one molecule in atomic mass units; molar mass is the mass of one mole in grams. So water is 18.015 amu per molecule and 18.015 g/mol.
How do I enter parentheses in a formula?
Type them directly with a subscript multiplier, like Ca(OH)2 or (NH4)2SO4. Everything inside the parentheses is multiplied by the number that follows before being added to the total.
Why must I capitalize element symbols correctly?
Because capitalization distinguishes elements. 'Co' is cobalt while 'CO' is carbon monoxide (carbon + oxygen). Using the wrong case gives a wrong result or an unknown-element error.
Does this handle hydrates like CuSO4ยท5H2O?
Not with the dot notation. Write out all the atoms instead โ for the pentahydrate that means adding the water atoms to the formula โ or compute the anhydrous salt and the water separately and add them.
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