Oxidation State Calculator — Redox & Oxidation Number SolverOxidation Numbers · Redox Rules · Ionic Compounds · Polyatomic Ions · Half-Reactions
Use this free Oxidation State Calculator to instantly determine the oxidation number of every element in any chemical compound, ionic formula, or polyatomic ion by systematically applying the standard oxidation state rules of inorganic chemistry: free elements always have oxidation state = 0 · monatomic ions = their ionic charge · oxygen = −2 (except peroxides −1 and OF₂ +2) · hydrogen = +1 (except metal hydrides −1) · sum of oxidation states = overall charge of compound or ion — giving you a complete, step-by-step oxidation number solution for any formula you enter.
This online redox calculator is applied extensively across inorganic and physical chemistry: identifying oxidizing and reducing agents in redox reactions, balancing redox equations using the half-reaction method, electrochemistry and galvanic cell analysis, transition metal oxidation state determination (Fe²⁺/Fe³⁺, Mn²⁺/MnO₄⁻, Cr³⁺/Cr₂O₇²⁻), corrosion and oxidation mechanism analysis, and organic chemistry oxidation level calculations. Trusted by A-Level, AP Chemistry, IB Chemistry, JEE, and NEET students, undergraduate chemistry learners, and research chemists for fast, rule-based oxidation number assignment and redox reaction analysis — replacing tedious manual oxidation state calculations with instant, accurate results.
Related Science & Chemistry Calculators
Molarity Calculator
Calculate molarity and solution concentration.
Stoichiometry Calculator
Solve chemical equations and mole ratios.
Ideal Gas Law Calculator
Calculate pressure, volume, temperature, and moles.
pH Calculator
Compute acidity and alkalinity of solutions.
Thermodynamics Calculator
Analyze energy, heat, and work in chemical systems.
Redox Calculator — Oxidation States, Half-Reactions, and Cell Potential
Redox reactions involve electron transfer between species — one species is oxidized (loses electrons, increases oxidation state) and another is reduced (gains electrons, decreases oxidation state). Identifying what is oxidized and reduced requires assigning oxidation states to every atom using the standard rules: pure elements are 0, oxygen is -2 (except peroxides), hydrogen is +1 (except metal hydrides), and fluorine is always -1. The redox calculator assigns oxidation states from chemical formulas and identifies the oxidizing and reducing agents in a reaction.
Balancing redox reactions requires the half-reaction method in acidic or basic solution. In acidic solution: balance atoms (adding H⁺ and H₂O), then balance charge by adding electrons to each half-reaction, then multiply to equalize electrons transferred. The permanganate/oxalate reaction in acidic solution requires multiplying the oxidation half by 5 and the reduction half by 2 to equalize the 10 electrons transferred: 2MnO₄⁻ + 5C₂O₄²⁻ + 16H⁺ → 2Mn²⁺ + 10CO₂ + 8H₂O. The calculator performs systematic half-reaction balancing for any redox pair in specified pH conditions.
Electrochemical cell potential E°cell = E°cathode - E°anode determines whether a redox reaction is spontaneous under standard conditions. Positive E°cell means spontaneous (ΔG = -nFE°cell < 0). The zinc-copper cell has E°cell = +0.34 - (-0.76) = +1.10V — a positive value confirming zinc spontaneously reduces copper ions. The calculator retrieves standard reduction potentials for common half-reactions and computes cell potential, ΔG°, and the equilibrium constant K for the overall redox reaction.