Calculadora de Massa Molecular
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
MM = m / n
About this calculator
The Molecular Mass Calculator is a practical tool for chemistry students and professionals. It determines the molecular mass in grams per mole (g/mol) from two values: the mass of the substance (in grams) and the amount of substance (in moles). The calculation is based on the fundamental stoichiometric relationship where molecular mass equals mass divided by amount of substance.
The operation is simple: enter the mass of the sample and the corresponding number of moles. The formula applied is MM = m / n, where MM is the molecular mass, m is the mass, and n is the amount of substance. For example, if you have 18 grams of water and 1 mole, the result will be 18 g/mol, which is the molecular mass of water.
This calculator is useful in various situations: to verify experimental results, prepare solutions with specific concentrations, or solve stoichiometry problems in exams and academic work. It also helps identify unknown substances by comparing the calculated value with known molecular masses.
Important precautions: ensure that mass and amount of substance are in the correct units (grams and moles). Very small or large values may require scientific notation. Remember that the calculated molecular mass is an average weighted by isotopes, so it may vary slightly depending on the isotopic composition of the sample.
Frequently asked questions
What if I don't know the amount of substance (moles)?
You need to calculate the moles first, usually by dividing the mass by the molar mass of the substance. This calculator requires both values to work.
Can I use units other than grams and moles?
No, the calculator expects mass in grams and amount in moles. If you have other units, convert them first (e.g., kg to g, kmol to mol).
Is the calculated molecular mass exact?
It is as accurate as the rounding of the input values. Remember that atomic masses are averages, so small variations may occur.
Does this calculator work for ionic compounds?
Yes, the concept of molecular mass applies to any substance, including ionic compounds. In that case, it is often called formula mass.
What is the difference between molecular mass and molar mass?
Molecular mass is the mass of a molecule in atomic mass units (u), while molar mass is the mass of one mole in g/mol. Numerically, they are the same.