Calculate the molecular weight (molar mass) of any chemical compound from its molecular formula. Enter a chemical formula and get instant results with detailed atomic composition.
Molecular weight, also referred to as molar mass, is a fundamental concept in chemistry that represents the mass of one mole of a substance. It is typically expressed in grams per mole (g/mol) and is calculated by summing the atomic weights of all atoms in a molecule according to its chemical formula.
Understanding molecular weight is essential for stoichiometric calculations, determining chemical quantities, preparing solutions, and analyzing chemical reactions. Our calculator provides not only the total molecular weight but also the percentage composition of each element in the compound.
Atom: The basic particle of chemical elements consisting of a nucleus containing protons and neutrons, surrounded by electrons. Each element is distinguished by its number of protons.
Isotope: Atoms of the same element with the same number of protons but different numbers of neutrons. Different isotopes have different atomic masses.
Mole (mol): A unit of measurement representing exactly 6.02214076 × 10²³ particles (Avogadro's number), whether atoms, molecules, or ions.
Molecule: A group of two or more atoms held together by chemical bonds, representing the smallest unit of a chemical compound.
Atomic Weight: The weighted average mass of all isotopes of an element, expressed relative to 1/12 of the mass of carbon-12.
Molecular Weight: The sum of atomic weights of all atoms in a molecule, expressed in atomic mass units (amu) or grams per mole (g/mol).
To calculate molecular weight, follow these systematic steps:
1. Identify the elements: Determine all elements present in the chemical formula
2. Count the atoms: Count how many atoms of each element are present
3. Find atomic weights: Look up the standard atomic weight for each element
4. Calculate contributions: Multiply each element's atomic weight by its number of atoms
5. Sum the total: Add all elemental contributions to get the molecular weight
Elements present: Hydrogen (H) and Oxygen (O)
Atom count: 2 Hydrogen atoms, 1 Oxygen atom
Atomic weights: H = 1.008 g/mol, O = 15.999 g/mol
Calculation: (2 × 1.008) + (1 × 15.999) = 2.016 + 15.999 = 18.015 g/mol
Result: Molecular weight of H₂O = 18.015 g/mol
Elements present: Carbon (C), Hydrogen (H), and Oxygen (O)
Atom count: 6 Carbon atoms, 12 Hydrogen atoms, 6 Oxygen atoms
Atomic weights: C = 12.011 g/mol, H = 1.008 g/mol, O = 15.999 g/mol
Calculation: (6 × 12.011) + (12 × 1.008) + (6 × 15.999) = 72.066 + 12.096 + 95.994 = 180.156 g/mol
Result: Molecular weight of C₆H₁₂O₆ = 180.156 g/mol
| Element | Symbol | Atomic Weight (g/mol) | Element | Symbol | Atomic Weight (g/mol) |
|---|---|---|---|---|---|
| Hydrogen | H | 1.008 | Sodium | Na | 22.990 |
| Helium | He | 4.003 | Magnesium | Mg | 24.305 |
| Lithium | Li | 6.940 | Aluminum | Al | 26.982 |
| Carbon | C | 12.011 | Silicon | Si | 28.085 |
| Nitrogen | N | 14.007 | Phosphorus | P | 30.974 |
| Oxygen | O | 15.999 | Sulfur | S | 32.060 |
| Fluorine | F | 18.998 | Chlorine | Cl | 35.450 |
| Neon | Ne | 20.180 | Potassium | K | 39.098 |
| Calcium | Ca | 40.078 | Iron | Fe | 55.845 |
| Copper | Cu | 63.546 | Silver | Ag | 107.868 |
Molecular weight calculations are fundamental to many areas of chemistry and related fields. In analytical chemistry, molecular weight helps identify unknown compounds and verify sample purity. Pharmaceutical chemists use molecular weight for drug formulation, dosage calculations, and quality control.
In biochemistry, molecular weight is crucial for understanding protein structure, enzyme kinetics, and metabolic pathways. Environmental chemists rely on molecular weight data for pollution monitoring, risk assessment, and remediation strategies. Industrial chemists use these calculations for process optimization, product development, and material characterization.
Students and researchers use molecular weight calculations for stoichiometry problems, solution preparation, and experimental design. Understanding molecular weight relationships helps in predicting physical properties, reaction yields, and chemical behavior of substances.