Select elements and set quantities to compute molar mass (g/mol)
Powered by standard atomic weights · Chemistry Tools
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When you’re working with chemical reactions, understanding how much of each substance you need is essential. The bridge between the microscopic world of atoms and molecules and the macroscopic world of grams and kilograms is molar mass, the mass of one mole of a substance. Whether you’re balancing equations in the lab, preparing solutions in a classroom, or simply curious about the composition of a compound, knowing the molar mass is a fundamental skill in chemistry.
This molar mass calculator lets you build any chemical formula by selecting elements from the periodic table and setting their quantities. The tool computes the total molar mass in grams per mole, showing you a detailed breakdown of each element’s contribution. Choose from common examples like water, sodium chloride, or glucose, or build your own custom compound. Whether you’re a student checking homework, a teacher preparing classroom materials, or a researcher working in the lab, this calculator delivers accurate results instantly. All processing runs locally in your browser, keeping your data private.
Select an element from the dropdown menu in the first row, choose from a comprehensive list of elements with their symbols and names.
Enter the quantity of that element in the formula, the number of atoms of that element in your compound.
Add more elements as needed using the “Add Element” button, build any compound by adding rows.
Click one of the example buttons to quickly load common compounds like H₂O, NaCl, or C₆H₁₂O₆.
Review the molar mass result, the formula display, and the detailed element breakdown table.
Use the Copy button to save results or Share to send them to others.
The calculator applies the standard method for calculating molar mass, which is the sum of the atomic masses of all atoms in a chemical formula. The atomic mass of each element is multiplied by the number of atoms of that element in the compound.
Formula: Molar Mass = Σ (Atomic Massᵢ × Quantityᵢ)
For a compound with elements E₁, E₂, …, Eₙ and quantities q₁, q₂, …, qₙ:
Formula: M = (a₁ × q₁) + (a₂ × q₂) + … + (aₙ × qₙ)
Where aᵢ is the atomic mass of element i in grams per mole, and qᵢ is the number of atoms of that element in the formula.
For example, water (H₂O): M = (1.008 × 2) + (15.999 × 1) = 2.016 + 15.999 = 18.015 g/mol.
The calculator uses standard atomic weights from IUPAC, providing accurate molar mass values for any compound you build.
Let’s calculate the molar mass of glucose, one of the most important carbohydrates in biology.
Step 1: Identify the elements and their quantities
Carbon (C): 6 atoms
Hydrogen (H): 12 atoms
Oxygen (O): 6 atoms
Step 2: Look up the atomic masses
Carbon: 12.011 g/mol
Hydrogen: 1.008 g/mol
Oxygen: 15.999 g/mol
Step 3: Multiply each atomic mass by its quantity
Carbon: 12.011 × 6 = 72.066 g/mol
Hydrogen: 1.008 × 12 = 12.096 g/mol
Oxygen: 15.999 × 6 = 95.994 g/mol
Step 4: Sum the contributions
Total = 72.066 + 12.096 + 95.994 = 180.156 g/mol
Interpretation: The molar mass of glucose is approximately 180.16 g/mol. This means one mole of glucose molecules weighs 180.16 grams. This value is essential for preparing solutions, calculating reaction yields, and understanding the stoichiometry of biochemical reactions.
Computes molar mass instantly for any compound by selecting elements and setting quantities.
Shows a detailed breakdown table with each element’s contribution to the total.
Includes example buttons for common compounds like water, salt, and glucose.
Supports any number of elements, build formulas as simple or complex as you need.
Uses standard atomic weights from IUPAC for accurate results.
Updates results instantly as you change selections or quantities.
Runs entirely client-side with no server communication, keeping your data private.
Free to use on any device with responsive design.
Molar mass is the mass of one mole of a substance, measured in grams per mole (g/mol). It’s calculated by summing the atomic masses of all atoms in a chemical formula.
To calculate molar mass, multiply the atomic mass of each element by the number of atoms of that element in the formula, then sum all the contributions. The calculator does this automatically.
The molar mass of water is 18.015 g/mol. This is calculated as (1.008 × 2) + 15.999 = 18.015 g/mol.
The molar mass of sodium chloride is 58.44 g/mol. This is calculated as 22.990 + 35.45 = 58.44 g/mol.
The molar mass of glucose is approximately 180.16 g/mol. This is calculated as (12.011 × 6) + (1.008 × 12) + (15.999 × 6) = 180.156 g/mol.
Molar mass and molecular weight are often used interchangeably, but molar mass has units of g/mol, while molecular weight is a dimensionless ratio. In practice, the numerical values are the same, but molar mass is the preferred term in chemistry.
Molar mass is essential for converting between mass and moles, which is critical for stoichiometry, solution preparation, and reaction calculations. It connects the microscopic world of atoms and molecules to the macroscopic world of grams and kilograms.
Yes, the calculator supports any compound with any number of elements. You can build complex formulas by adding rows for each element and setting the appropriate quantities.
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