Molecular Mass Calculator – Calculate Molar Mass of Any Compound
Calculate the molecular mass of any chemical compound by entering its formula. Our molecular mass calculator uses atomic weights to deliver accurate molar mass in g/mol instantly. Useful for chemistry students and lab professionals.
Molecular mass (or molar mass) is the sum of atomic masses of all atoms in a molecule. You express it in grams per mole (g/mol). The molar mass lets you convert between mass and moles of a substance.
How to Calculate Molar Mass
- Identify each element in the chemical formula
- Count the number of atoms of each element
- Find the atomic mass of each element from the periodic table
- Multiply atomic mass by the number of atoms
- Add all the masses together
Example: Water (H₂O)
2 H atoms × 1.008 g/mol = 2.016 g/mol
1 O atom × 15.999 g/mol = 15.999 g/mol
Total = 18.015 g/mol
Example: Glucose (C₆H₁₂O₆)
6 C atoms × 12.01 g/mol = 72.06 g/mol
12 H atoms × 1.008 g/mol = 12.096 g/mol
6 O atoms × 15.999 g/mol = 95.994 g/mol
Total = 180.15 g/mol
Enter a formula and calculate to see the breakdown
Enter the chemical formula
Use standard notation: H2O for water, C6H12O6 for glucose, H2SO4 for sulfuric acid.
Click Calculate Molar Mass
The calculator parses the formula and looks up atomic masses from the periodic table.
View the breakdown
See the total molar mass and how much each element contributes.
| Element | Symbol | Atomic Mass (g/mol) |
|---|---|---|
| Hydrogen | H | 1.008 |
| Carbon | C | 12.01 |
| Nitrogen | N | 14.01 |
| Oxygen | O | 15.999 |
| Sodium | Na | 22.99 |
| Chlorine | Cl | 35.45 |
| Iron | Fe | 55.85 |
Molar mass connects the microscopic world of atoms to the macroscopic world of grams. It tells you how much one mole (6.022 × 10²³ particles) of a substance weighs.
Converting grams to moles
moles = mass (g) / molar mass (g/mol). Essential for stoichiometry calculations.
Preparing solutions
To make 1 L of 1 M NaCl, you need 58.44 g (the molar mass of NaCl).
Determining empirical formulas
Compare mass percentages to find the simplest whole-number ratio of atoms.
How do I calculate molar mass manually?
List each element in the formula. Find its atomic mass on the periodic table. Multiply by the number of atoms (subscript). Add all the masses. For H₂O: (2 × 1.008) + (1 × 15.999) = 18.015 g/mol.
What's the difference between molecular mass and molar mass?
Molecular mass is the mass of one molecule (in atomic mass units, amu). Molar mass is the mass of one mole of molecules (in g/mol). Numerically they're the same, but units differ.
How do I handle parentheses in formulas?
Multiply everything inside parentheses by the subscript outside. For Ca(OH)₂: Ca = 40.08, O = 2 × 16.00 = 32.00, H = 2 × 1.008 = 2.016. Total = 74.10 g/mol.
Why aren't atomic masses whole numbers?
Atomic masses are weighted averages of all naturally occurring isotopes. Carbon is 12.01 because it's mostly C-12 with about 1% C-13. The average reflects natural abundance.
Can this calculator handle complex formulas?
It handles standard formulas like H2SO4, C6H12O6, and Ca(OH)2. For very complex formulas with nested parentheses or hydrates (like CuSO4·5H2O), calculate each part separately.
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