Enter the molecular weight and the number of electrons lost or gained by one molecule to calculate the equivalent weight.

Equivalent Weight Formula

The following formula is used to calculate an equivalent weight.

EW = MW / ΔE

  • Where EW is the equivalent weight
  • MW is the molecular weight
  • ΔE is the number of electrons gained or lost by one molecule

Equivalent Weight Definition

Equivalent weight is the total mass that combines with or is equivalent to one gram of hydrogen. In other words, the ratio of molecular weight to valence electrons.

What are the units for equivalent weight?

The most common units for equivalent weight are grams and Amu’s but it can technically be any unit of mass as long as the ratio is a ratio of the molecular weight to the change in electrons.

Is equivalent weight and equivalent mass the same?

Equivalent weights and equivalent masses are similar but different. Equivalent weight is a ratio of weight to change in electrons while equivalent mass is the ratio of mass to change in electrons. Mass is a measure of the total substance and weight is a measure of the force of gravity on that object due to mass.

Equivalent Weight Example

How to calculate an equivalent weight?

  1. First, determine the molecular weight.

    Calculate or determine the molecular weight.

  2. Next, determine the number of electrons gained or lost.

    Calculate the number of valence electrons or change in electrons.

  3. Finally, calculate the equivalent weight.

    Calculate the equivalent weight.


What is an equivalent weight?

Equivalent weight is a measure of the ratio of molecular weight to the change in electrons during the combination of molecules.

equivalent weight calculator
equivalent weight formula