Molecular Weight Calculator
Use standard chemical notation. Examples: H2O, NaCl, C6H12O6, Ca(OH)2
Quick Examples
How to Use the Molecular Weight Calculator
Enter the chemical formula in the input field using standard notation (e.g., H2O for water).
Use parentheses for complex compounds (e.g., Ca(OH)2 for calcium hydroxide).
Click "Calculate Molecular Weight" to get the result in g/mol.
View the detailed breakdown to understand how the calculation was performed.
Try the quick examples to see how different compounds are calculated.
Mathematical Foundation
The molecular weight (also called molar mass) of a compound is calculated by summing the atomic weights of all atoms in the molecular formula, multiplied by their respective quantities.
Formula:
MW = Σ(n × AW)
Where: MW = Molecular Weight, n = number of atoms, AW = Atomic Weight
For example, water (H2O) has a molecular weight of:
MW = (2 × 1.008) + (1 × 15.999) = 18.015 g/mol
Frequently Asked Questions
What is the difference between molecular weight and molar mass?
Technically, molecular weight is dimensionless while molar mass has units (g/mol). However, they have the same numerical value and are often used interchangeably in chemistry.
How accurate are the atomic weights used?
Our calculator uses IUPAC standard atomic weights with precision to at least 4 decimal places, suitable for most academic and professional calculations.
Can I calculate molecular weight for ionic compounds?
Yes! While ionic compounds don't have true "molecules," you can still calculate their formula weight using the same method (e.g., NaCl, CaCO3).
What if my formula contains brackets or complex groups?
Use parentheses for complex groups. For example, calcium hydroxide is Ca(OH)2, which means one calcium atom and two hydroxide groups.