Created By : Rina Nayak

Reviewed By : Phani Ponnapalli

Last Updated : May 25, 2023

Oxidation Number Calculator is a free online tool that displays the oxidation number of a chemical compound. This calculator makes it easy for you to calculate the oxidation number of the given input chemical compound. Enter input and hit on the calculate button to get the oxidation number as output within no time.

Enter chemical equation

Procedure to Find Oxidation Number of an Element in Chemical Compound

  • Let us take any chemical compound.
  • Go through the rules listed below to determine the oxidation numbers.
  • According to those rules write the oxidation number of that element above the symbol and total number of atoms below the symbol.
  • Evaluate the oxidation number and give the output answer.

FAQs on Oxidation Number Calculator

1. What is the difference between oxidation state and oxidation number?

Oxidation state and oxidation number are the quantities that commonly equal the same value for atoms in a molecule and are often used interchangeably. Oxidation state refers to the degree of oxidation of an atom in a molecule. Oxidation numbers are used in coordination complex chemistry.

2. What does the Oxidation Number means?

The oxidation number is a number which is generally assigned to the atoms of chemical substance. it helps to keep track of electrons in an atom. It can be positive , negative or zero. Oxidation number indicates the lose or gain of electrons in an atom.

3. What is oxidation on the basis of oxidation number?

Oxidation is the loss of one or more electrons by an atom. If the oxidation number of an element increases, it says there is a loss of electrons and that element is being oxidized.

4. What is the oxidation number of Na2SO4?

We know that oxidation number of group 1 element in the compound is +1.

So, Na oxidation number is +1.

A total of 2 elements are there in the given compound. That means +2.




The oxidation number of O in compounds is -2.

We have 4 O atoms in given compound. So it is -8.

   +1    -2


   +2   -8

The sum of oxidation numbers of all atoms is zero. So Na number becomes +6.

   +1    -2


  +2  +6  -8

Oxidation number of O is -8, Na is +2, S is +6 in the given compound.

Rules to Compute the Oxidation Numbers

1. Oxidation number of a free element is zero.

2. Oxidation number of a monatomic ion is equal to charge of that ion.

3. The oxidation number of Hydrogen H is +1, but it is -1 when combined with less electronegative elements.

4. Oxidation number of Oxygen O in compounds is -2, but it is -1 in peroxides.

5. Oxidation number of Group 1 element in compound is +1.

6. Oxidation number of Group 2 element in compound is +2.

7. Oxidation number of Group 17 element in a binary compound is -1.

8. The sum of oxidation numbers of all the atoms in a neutral compound is 0.

9. The sum of oxidation numbers in a poly atomic ion is equal to the charge of ion.


Question: What is the oxidation number of Cr in CrCl3?


Given compound is CrCl3

As per the rule 7, oxidation number of Chlorine Cl is -1.


This gives CrCl3

We have 3 Cl atoms. So its oxidation number becomes -3.




Rule 8 says that, sum of oxidation numbers of all atoms is zero.



 +3 -3

We have only one Cr atom, so its oxidation number is +3.

Finally, the oxidation number of Cr in CrCl3 is +3.

Have a look at Chemistrycalc.Com to get an idea on the various math concepts and its calculators. These calculators give instant results easily.