Molecular Weight Calculator
Calculate molecular weights from chemical formulas with support for complex notation including parentheses and subscripts.
Molecular Weight Calculator
Use standard chemical notation: H2O, CaCO3, Ca(OH)2, Al2(SO4)3
98.0720 g/mol
Molecular Weight
Elemental Composition
H×2
1.008 g/mol each
Total: 2.016 g/mol
S×1
32.060 g/mol each
Total: 32.060 g/mol
O×4
15.999 g/mol each
Total: 63.996 g/mol
Formula: H2SO4
Calculation: Sum of (atomic weight × count) for each element
Calculation: Sum of (atomic weight × count) for each element
Common Compounds
Click on a compound to load its formula:
H2O
Water
Water
H2SO4
Sulfuric Acid
Sulfuric acid
NaCl
Sodium Chloride
Table salt
CaCO3
Calcium Carbonate
Limestone
C6H12O6
Glucose
Glucose
C8H10N4O2
Caffeine
Caffeine
C9H8O4
Aspirin
Aspirin
NH3
Ammonia
Ammonia
CH4
Methane
Methane
CO2
Carbon Dioxide
Carbon dioxide
C2H5OH
Ethanol
Ethanol
C6H6
Benzene
Benzene
What is Molecular Weight Calculator?
Understanding Molecular Weight
Molecular weight (also called molecular mass) is the sum of the atomic weights of all atoms in a molecule. It is expressed in atomic mass units (amu) or grams per mole (g/mol) and is fundamental to stoichiometric calculations in chemistry.
Chemical Formula Notation
Element Symbols
Use standard periodic table symbols: H (hydrogen), O (oxygen), Ca (calcium)
Subscripts (Numbers)
Indicate number of atoms: H₂O means 2 hydrogen atoms and 1 oxygen atom
Parentheses
Group atoms: Ca(OH)₂ means 1 calcium, 2 oxygen, and 2 hydrogen atoms
Calculation Process
- Parse the chemical formula to identify all elements and their quantities
- Look up the atomic weight of each element from the periodic table
- Multiply each element's atomic weight by its quantity in the molecule
- Sum all the products to get the total molecular weight
Applications
- •Stoichiometry: Calculate reactant and product quantities in chemical reactions
- •Solution Preparation: Determine masses needed for specific molar concentrations
- •Analytical Chemistry: Identify unknown compounds from mass spectrometry data
- •Pharmaceutical: Calculate drug dosages and formulations
Example Calculations
Water (H₂O):
2 × H (1.008) + 1 × O (15.999) = 18.015 g/mol
2 × H (1.008) + 1 × O (15.999) = 18.015 g/mol
Sulfuric Acid (H₂SO₄):
2 × H (1.008) + 1 × S (32.06) + 4 × O (15.999) = 98.078 g/mol
2 × H (1.008) + 1 × S (32.06) + 4 × O (15.999) = 98.078 g/mol
Calcium Hydroxide [Ca(OH)₂]:
1 × Ca (40.078) + 2 × O (15.999) + 2 × H (1.008) = 74.092 g/mol
1 × Ca (40.078) + 2 × O (15.999) + 2 × H (1.008) = 74.092 g/mol
FAQ - Molecular Weight Calculator
Molecular weight and molar mass are numerically identical but have different units. Molecular weight is expressed in atomic mass units (amu) and refers to the mass of a single molecule. Molar mass is expressed in g/mol and refers to the mass of one mole of molecules.