Molecular Weight Calculator
Calculate the molecular weight of chemical compounds from their formulas.
A molecular weight calculator computes the molar mass of chemical compounds by summing the atomic weights of each element in the formula.
Examples
Water (H2O)
Glucose (C6H12O6)
Frequently Asked Questions
What is molecular weight vs molar mass?
How do I enter formulas with parentheses?
Quick Tips
- •Capitalize element symbols correctly — Na is sodium, NA would be nitrogen + argon.
- •For hydrates like CuSO4·5H2O, calculate the anhydrous and water portions separately and add them.
A molecular weight calculator computes the molar mass of chemical compounds by summing the atomic weights of each element in the formula.
How to Use This Calculator
Enter a chemical formula using standard notation (e.g. H2O, NaCl, C6H12O6, Ca(OH)2). The calculator parses the formula and sums atomic weights from the periodic table to find the molecular weight.
Understanding the Formula
Molecular Weight = Sum of (Atomic Weight x Count) for each element in the formula. Atomic weights are from the IUPAC standard periodic table.
Examples
Water (H2O)
H: 2 x 1.008 = 2.016. O: 1 x 15.999 = 15.999. Total: 18.015 g/mol.
Glucose (C6H12O6)
C: 6 x 12.011 = 72.066. H: 12 x 1.008 = 12.096. O: 6 x 15.999 = 95.994. Total: 180.156 g/mol.
Frequently Asked Questions
What is molecular weight vs molar mass?
Molecular weight (or molecular mass) and molar mass are numerically equal but have different units. Molecular weight is in atomic mass units (amu or Da), while molar mass is in grams per mole (g/mol).
How do I enter formulas with parentheses?
Use standard chemical notation, e.g. Ca(OH)2 for calcium hydroxide. The calculator expands parenthetical groups by the subscript that follows.
Assumptions & Limitations
- Uses IUPAC 2021 standard atomic weights, which represent natural isotopic mixtures.
- Assumes standard chemical notation with proper capitalization (e.g., Co for cobalt, CO for carbon monoxide).