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Free oxidation number calculator & oxidation state calculator. Calculate oxidation numbers in compounds, find oxidation states, and solve redox reactions with step-by-step solutions. Our chemistry calculator helps you master oxidation-reduction chemistry and electron transfer concepts.
Last updated: February 2, 2026
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Enter a common compound formula
Oxidation number of S in H2SO4
+6
Calculation Steps:
Explanation:
In H2SO4, S has an oxidation number of +6
Oxidation Number Rules:
Method
Rules-Based Analysis
Apply systematic rules to determine oxidation numbers
Analysis
Electron Transfer
Identify oxidation and reduction in chemical reactions
Technique
Sum = Charge
Use algebra to find oxidation numbers in complex compounds
Database
H₂SO₄, KMnO₄, HNO₃
Instant results for commonly studied compounds
Elements
S, N, Mn, Cr, Fe
Determine oxidation states for transition metals and more
Rules applied
6 Key Rules
Systematic approach using established chemistry rules
Oxidation number of sulfur in H₂SO₄:
Oxidation State of S
+6
Calculated: 2(+1) + x + 4(-2) = 0
Our oxidation number calculator uses systematic chemistry rules and algebraic methods to determine oxidation states of elements in compounds. The calculator applies established oxidation number rules and solves equations to find oxidation states in even the most complex compounds.
Rule 1: Free elements = 0Rule 2: Monoatomic ions = ion chargeRule 3: Group 1 = +1, Group 2 = +2Rule 4: Oxygen = -2 (usually)Rule 5: Hydrogen = +1 (usually)Rule 6: Sum of oxidation numbers = total chargeThese fundamental rules govern oxidation number assignment. For neutral compounds, the sum equals zero; for ions, it equals the ion charge. The algebraic method uses these rules to solve for unknown oxidation states.
Shows electron transfer and oxidation state changes in redox reactions
The algebraic method is powerful for finding unknown oxidation numbers. Set up an equation where the sum of all oxidation numbers equals the total charge (0 for neutral molecules, the ion charge for polyatomic ions). Solve for the unknown variable representing the oxidation number you need.
Need help with other chemistry calculations? Check out our balance equation calculator and mole calculator.
Get Custom Calculator for Your Chemistry CourseResult: The oxidation number of sulfur in H₂SO₄ is +6
Sulfur is in its highest common oxidation state in sulfuric acid
Algebraic method
(+1) + x + 3(-2) = 0 → x = +5
Potassium permanganate
(+1) + x + 4(-2) = 0 → x = +7
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