THE NUMORIX GUIDE
How to use the Molar Mass Calculator
Last reviewed September 14, 2026
What this calculator does
Parse an element formula, count each element including parenthesized groups, multiply each count by the engine's atomic weight, and sum contributions to grams per mole.
Formula and method
Parse an element formula, count each element including parenthesized groups, multiply each count by the engine's atomic weight, and sum contributions to grams per mole.
Variables and inputs
Chemical formula defaults to H2O. The parser accepts element symbols, integer subscripts, parentheses, and a dot separator for hydrate-like text; output is in g/mol.
Worked example
For H2O: H count=2 contributes 2*1.008=2.0160 g/mol; O count=1 contributes 1*15.999=15.9990 g/mol; total molar mass = 18.0150 g/mol.
How to interpret the result
Molar mass is the mass of one mole of formula units. It lets a measured mass convert to amount of substance through n=m/M.
Common mistakes to avoid
Read subscripts as multipliers for the preceding element or group, and distinguish Co from C plus O. Do not use a coefficient outside a formula as if it changed the formula's molar mass unless you are calculating a multiple of formula units.
Assumptions and limitations
Atomic weights are fixed rounded values in the engine and do not represent isotope-specific or sample-specific composition. The parser supports integer counts but not every chemistry notation, charge, bracket, or fractional hydrate convention.
Practical use and checks
The Molar Mass Calculator adds the atomic weights represented by a chemical formula. Enter H2O as a check; the result should be about 18.015 grams per mole from two hydrogen atoms and one oxygen atom. Enter Ca(OH)2 as a second check; calcium plus two oxygen atoms and two hydrogen atoms should produce about 74.092 g/mol. Parentheses matter because the subscript 2 applies to the entire hydroxide group, not just the final hydrogen. Use molar mass to convert between grams and moles after the formula and sample identity are established. For example, 36.03 g of water is approximately 2.00 mol because 36.03 divided by 18.015 is 2. The engine accepts element symbols, numeric subscripts, and parenthesized groups, but it does not infer oxidation state, isotope abundance, charge, phase, or a missing subscript. Hydrate notation and middle dots are handled as a parsing convention, not as a guarantee that every chemical formula style is accepted. Atomic weights are fixed approximations, so isotope-enriched material can differ. An invalid symbol or unmatched parenthesis should be treated as an input error, not as a zero-mass compound. Keep formula, purity, and atomic-weight convention with any mass calculation used for a laboratory preparation.