Molecular Formula Calculator
Explore the relationship between molecular formulas and empirical formulas. Enter a molecular formula to calculate its molecular weight, then compare with the empirical formula weight to find the multiplication factor n. This tool helps you understand how molecular formulas relate to empirical formulas through molecular weight ratios.
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Molecular Formula Weight Computation
See how the molecular formula determines the molecular weight.
A molecular formula specifies the exact number of each atom in a molecule. Glucose's molecular formula C₆H₁₂O₆ tells us each molecule has 6 carbons, 12 hydrogens, and 6 oxygens — giving a molecular weight of 180.16 g/mol.
The empirical formula CH₂O represents the simplest ratio (1:2:1). The empirical formula weight is 30.03 g/mol. The ratio n = 180.16/30.03 = 6 confirms the molecular formula is 6 times the empirical formula.
This relationship is fundamental in chemistry: elemental analysis gives the empirical formula, mass spectrometry gives the molecular weight, and dividing MW by EFW yields n — revealing the true molecular formula.
Atomic Weights for Formula Calculations
Atomic weights of elements commonly found in molecular formulas.
Molecular formulas in organic chemistry primarily use C, H, O, N, S, and P — the elements of life. Halogenated compounds add F, Cl, Br, or I. Each element's standard atomic weight contributes to the molecular formula weight.
Knowing atomic weights helps estimate molecular weights quickly: each CH₂ unit adds ~14 g/mol, each OH group adds ~17 g/mol, each NH₂ group adds ~16 g/mol. These shortcuts help verify calculated molecular weights.
Explore the element cards below to see atomic weights used in molecular formula calculations.
Molecular vs Empirical Formula
Understand the relationship between molecular and empirical formulas.
Enter the Molecular Formula
Type the true molecular formula of your compound — the one showing the actual number of each atom in a single molecule. For glucose, the molecular formula is C₆H₁₂O₆ (not the empirical formula CH₂O). The calculator uses this exact formula to compute the molecular weight.
Molecular Formula Examples
Click to see molecular formulas and their relationship to empirical formulas.
Molecular Formula FAQ
Questions about molecular formulas, empirical formulas, and their relationship.