Molecular Formula Calculator

Calculate the molecular formula from empirical formula mass and molar mass. Find the multiplier to convert empirical to molecular formula.

g/mol
g/mol

Quick Facts

Formula Relationship
Molecular = n x Empirical
n is always a whole number
Example: Glucose
CH2O to C6H12O6
Multiplier n = 6
Empirical Formula
Simplest ratio
Smallest whole number ratio
Molecular Formula
Actual atoms
Real number of atoms

Your Results

Calculated
Multiplier (n)
0
Molecular Formula = n x Empirical Formula
Empirical Mass
0 g/mol
Input value
Molar Mass
0 g/mol
Input value

Key Takeaways

  • The molecular formula is a whole number multiple of the empirical formula
  • Calculate n by dividing molar mass by empirical formula mass
  • The multiplier n should always round to a whole number
  • Molecular formula shows actual atoms; empirical shows simplest ratio

About the Molecular Formula Calculator

This molecular formula calculator helps you determine the molecular formula of a compound when you know the empirical formula mass and the actual molar mass. The molecular formula represents the actual number of atoms of each element in a molecule, while the empirical formula shows only the simplest whole-number ratio.

The Formula

n = Molar Mass / Empirical Formula Mass
n = Multiplier (whole number)
Molar Mass = Actual molecular mass (g/mol)
Empirical Mass = Mass of empirical formula (g/mol)

Example: Finding the Molecular Formula of Glucose

Empirical Formula CH2O
Empirical Mass 30.03 g/mol
Molar Mass 180.18 g/mol

n = 180.18 / 30.03 = 6, so the molecular formula is C6H12O6

How to Use This Calculator

1

Calculate Empirical Formula Mass

Add up the atomic masses of all atoms in your empirical formula. For CH2O: C(12.01) + H2(2.02) + O(16.00) = 30.03 g/mol

2

Enter the Molar Mass

Enter the actual molar mass of the compound (usually given in the problem or determined experimentally).

3

Calculate the Multiplier

Click Calculate to find n. Multiply each subscript in the empirical formula by n to get the molecular formula.

Applications

This molecular formula calculator is commonly used in:

  • Academic research and education
  • Professional chemistry work
  • Organic chemistry compound identification
  • Biochemistry and molecular biology
  • Pharmaceutical development

Frequently Asked Questions

The empirical formula shows the simplest whole-number ratio of atoms in a compound (e.g., CH2O), while the molecular formula shows the actual number of atoms in one molecule (e.g., C6H12O6 for glucose). The molecular formula is always a whole-number multiple of the empirical formula.

The multiplier should always be very close to a whole number. If it's not, check your calculations for errors. Small deviations (like 5.98 or 6.02) are due to rounding in atomic masses and should be rounded to the nearest whole number.

Add up the atomic masses of all atoms in the empirical formula. Use a periodic table to find atomic masses: Carbon = 12.01, Hydrogen = 1.008, Oxygen = 16.00, Nitrogen = 14.01, etc. Multiply each atomic mass by the number of atoms of that element.

Yes! When n = 1, the molecular formula equals the empirical formula. This occurs when the empirical formula already represents the actual molecular composition. Examples include water (H2O), carbon dioxide (CO2), and many small molecules.