Molar Mass Calculator
Compute the molecular weight of any chemical formula in g/mol with a full element-by-element breakdown.
| Element | Symbol | Count | Atomic Mass | Subtotal |
|---|
How to use the molar mass calculator
Molar mass (also called molecular weight) is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is found by adding the standard atomic weights of every atom in the chemical formula. Enter a formula above and the calculator parses it, looks up IUPAC standard atomic weights, and shows the total.
Type the formula using element symbols with correct capitalisation, e.g. NaCl not nacl. Numbers are subscripts: H2O means two hydrogen atoms.
Groups in brackets are multiplied by the following number, e.g. Ca(OH)2 has two OH groups. Nested brackets are supported.
The table shows each element, how many atoms appear, its atomic mass, and the subtotal. The total molar mass is shown in g/mol.
Frequently asked questions
What is molar mass and how is it calculated?
Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance, measured in grams per mole (g/mol). It is calculated by multiplying the standard atomic weight of each element by the number of its atoms in the formula, then adding all the contributions together. For example, water (H₂O) = 2 × 1.008 + 15.999 = 18.015 g/mol.
Is molar mass the same as molecular weight?
In everyday chemistry the two terms are used interchangeably and give the same number. Strictly, molecular weight (or relative molecular mass) is a dimensionless ratio relative to 1/12 of a carbon-12 atom, while molar mass carries the unit g/mol. For practical calculations, the numeric values are identical.
How do I enter hydrates like copper sulfate pentahydrate?
Use a dot to separate the water of crystallisation, exactly as written in textbooks: CuSO4.5H2O. The calculator treats the "5H2O" as five water molecules and adds their mass to the anhydrous salt. The result for CuSO₄·5H₂O is about 249.69 g/mol.
Which atomic weights does this calculator use?
It uses the IUPAC standard atomic weights (conventional values), for example H = 1.008, C = 12.011, O = 15.999, Na = 22.990, Cl = 35.45, S = 32.06, Cu = 63.546 and Ca = 40.078. All 118 elements are included. Values are rounded to standard precision, so small differences from other tables are normal.
Why is correct capitalisation important?
Element symbols are case-sensitive. "Co" is cobalt while "CO" is carbon monoxide (one carbon and one oxygen). Always write the first letter uppercase and any second letter lowercase, e.g. Na, Cl, Mg, Fe. The calculator will report an error for unrecognised symbols.