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Molecular Weight Calculator (Molar Mass)

Calculate molar mass and an element-by-element mass breakdown from a supported chemical formula and versioned atomic-mass data.

Your inputs

Case-sensitive symbols; parentheses, square brackets and hydrate dots are supported.

Calculations run in your browser. No account needed.

EXAMPLE RESULTCalculated locally
Molar mass
74.09 g/mol
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My workspace

Calculate with your inputs to save a result or compare scenarios.

Detailed breakdown

All 3 rows

The complete calculation, row by row.

Swipe or scroll horizontally for more columns.
Detailed breakdown · All 3 rows
ElementAtomsAtomic massContribution (g/mol)
Ca140.0840.08
O21632
H21.012.02

How it works

A useful distinction

Capitalization changes the substance

Co represents cobalt, while CO contains carbon and oxygen. These entries produce different element breakdowns and molar masses. Check the parsed element list before trusting a copied formula, especially when text formatting has changed its capitalization.

Entering a chemical formula accurately

The molecular-weight calculator interprets element symbols, counts, and supported grouping notation to build the formula mass. Capitalization matters because it helps identify the elements. Check that parentheses and multipliers describe the intended composition before calculating. The resulting mass reflects the atomic-weight data and formula entered; it does not identify an unknown sample or establish its purity.

Chemical formula: formula and assumptions

Molar mass = Σ(element count×listed atomic mass).

Uses the PubChem periodic table retrieved October 9, 2026. Isotopic labels and charged species are not supported.

Worked example

Using the Chemical formula example:

Inputs
Example compound
Custom formula
Chemical formula
Ca(OH)2
Method

Molar mass = Σ(element count×listed atomic mass).

Result

Example result

Molar mass: 74.09 g/mol

These are illustrative inputs. Change the values to explore a different scenario.

Formula references

References explain the underlying methods; they do not imply endorsement or individual professional review of Finflo.

Common questions

Does the formula parser support isotopic labels or charged species?

No. Those notations are outside the supported formula model and should not be treated as ordinary neutral-formula entries.

Why might a listed molar mass differ slightly from another table?

The result depends on the atomic-mass values and rounding used. This tool identifies the versioned reference table behind its calculation.

Prepared by Finflo. See our methodology and editorial policy.