Molar Mass Calculator
Calculate the molar mass of any chemical compound by selecting elements and atom counts. Free online chemistry calculator with element breakdown, percentage composition, and visual charts for students and lab professionals.
About This Calculator
The Molar Mass Calculator is a free online tool that computes the molar mass (molecular weight) of any chemical compound by summing the atomic masses of its constituent elements. Simply select elements from the periodic table and specify the number of atoms to instantly get the molar mass in grams per mole (g/mol), along with a detailed element breakdown and percentage composition. This calculator is ideal for chemistry students, teachers, researchers, and laboratory professionals who need quick and accurate molar mass calculations for stoichiometry, solution preparation, and chemical analysis.
The molar mass is calculated using the formula: μ = Σ (nᵢ × Aᵢ), where nᵢ is the number of atoms of element i and Aᵢ is its atomic mass in g/mol. Atomic masses follow the IUPAC standard periodic table values. The tool uses the chemical formula building approach — select elements from dropdown menus, set atom counts, and add or remove elements as needed to construct any compound from H₂ to complex organic molecules.
Quick Select buttons are provided for common molecules including water (H₂O, 18.015 g/mol), glucose (C₆H₁₂O₆, 180.156 g/mol), carbon dioxide (CO₂, 44.01 g/mol), methane (CH₄, 16.043 g/mol), ethanol (C₂H₅OH, 46.069 g/mol), ammonia (NH₃, 17.031 g/mol), sodium chloride (NaCl, 58.44 g/mol), sulfuric acid (H₂SO₄, 98.079 g/mol), nitric acid (HNO₃, 63.013 g/mol), and acetic acid (CH₃COOH, 60.052 g/mol). Results display as a breakdown table showing each element's mass contribution and percentage, plus bar and pie charts for visual analysis.
What is Molar Mass?
Molar mass (μ) is a physical property defined as the mass of a given substance divided by its amount of substance (moles). The SI unit for molar mass is kg/mol, but grams per mole (g/mol) is the most commonly used unit in chemistry. Molar mass is numerically equal to molecular weight but expressed in different units — molar mass in g/mol versus molecular weight in daltons (Da). Understanding molar mass is fundamental to stoichiometry, enabling chemists to convert between mass and moles in chemical equations, prepare solutions of precise concentration, determine empirical formulas from elemental analysis, and calculate gas properties using the ideal gas law.
Frequently Asked Questions
What is molar mass and how is it calculated?
Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol). It is calculated by summing the atomic masses of all atoms in the chemical formula. For example, water (H₂O) has a molar mass of 18.015 g/mol: 2 × 1.008 g/mol (hydrogen) + 1 × 16.00 g/mol (oxygen).
What is the difference between molar mass and molecular weight?
Molar mass and molecular weight are numerically equal but have different units. Molar mass is expressed in grams per mole (g/mol) and represents the mass of one mole of a substance. Molecular weight (or molecular mass) is expressed in daltons (Da) or unified atomic mass units (u) and represents the mass of a single molecule. For CO₂, the molar mass is 44.01 g/mol and the molecular weight is 44.01 u.
How do I use this molar mass calculator?
Select elements from the dropdown menu and specify the number of atoms for each element in your compound. You can also use the Quick Select buttons for common molecules like water (H₂O), glucose (C₆H₁₂O₆), or carbon dioxide (CO₂). Click Calculate to see the molar mass, element breakdown, and percentage composition with charts.
Can I calculate molar mass for complex compounds with many elements?
Yes, you can add up to 20 different elements to build any chemical compound. Use the + Add Element button to include more elements. The calculator supports all 118 elements from the periodic table with their standard atomic masses.
What is the molar mass of common compounds?
Water (H₂O): 18.015 g/mol. Carbon dioxide (CO₂): 44.01 g/mol. Sodium chloride (NaCl): 58.44 g/mol. Glucose (C₆H₁₂O₆): 180.156 g/mol. Sulfuric acid (H₂SO₄): 98.079 g/mol. Ammonia (NH₃): 17.031 g/mol. Methane (CH₄): 16.043 g/mol.
Why do I need to know the molar mass of a compound?
Molar mass is essential for converting between mass and moles in chemical reactions (stoichiometry), preparing solutions of specific concentration, determining empirical and molecular formulas, and calculating gas densities using the ideal gas law. It is a fundamental concept in chemistry used in laboratories, industry, and education worldwide.
How accurate are the atomic masses used in this calculator?
This calculator uses standard atomic weights from the IUPAC (International Union of Pure and Applied Chemistry) periodic table, which are accurate to at least three decimal places. Results are rounded to three decimal places, which is sufficient for most academic and laboratory applications.