Oxidation Number Calculator

The oxidation number of an element in a compound tells you how many electrons it has gained, lost, or shared — a key concept in chemistry for balancing redox reactions and understanding bonding. Enter a chemical formula (like H₂SO₄ or KMnO₄) into the Oxidation Number Calculator to see the oxidation states assigned to each element in the compound, along with the total charge. Also try the Empirical Formula Calculator.

Enter chemical formula using proper capitalization (H, O, Ca, Fe, etc.)

Results

Chemical Formula

--

Oxidation States

--

Total Charge

--

Results Table

Frequently Asked Questions

What is an oxidation state?

An oxidation state (also called oxidation number) is the hypothetical charge of an atom if all of its bonds to other atoms were fully ionic. It helps determine how electrons are distributed in chemical compounds. See also our Percent Ionic Character Calculator.

How are oxidation states calculated?

Oxidation states are calculated using specific rules: free elements have oxidation state 0, the sum of oxidation states in a neutral compound equals 0, hydrogen is usually +1, oxygen is usually -2, and alkali metals are +1.

What are the rules for assigning oxidation numbers?

Key rules include: free elements = 0, monatomic ions = their charge, hydrogen = +1 (except in hydrides where it's -1), oxygen = -2 (except in peroxides), and the sum must equal the compound's total charge.

How do I enter chemical formulas correctly?

Capitalize the first letter of each element symbol and use lowercase for remaining letters (Ca, Fe, Mg). Use parentheses for groups like Ca(OH)2 and numbers as subscripts like H2SO4. You might also find our Binding Energy per Nucleon Calculator useful.

Can this calculator handle complex organic compounds?

Yes, the calculator can process organic compounds using standard chemical formulas. For complex molecules, enter the molecular formula with proper element symbols and subscripts.

What does a negative oxidation state mean?

A negative oxidation state indicates the atom has gained electrons compared to its neutral state. Non-metals like oxygen and chlorine often have negative oxidation states in compounds.

Why might the total charge not equal zero?

If the total charge doesn't equal zero, you may have entered an ionic compound or made an error in the formula. Neutral compounds should always sum to zero, while ions will have a net charge.