Start with fixed rules
Oxygen is usually -2, fluorine is usually -1, Group 1 metals are usually +1, and Group 2 metals are usually +2.
P2 rule-based tool
Oxidation Number Calculator
Estimate oxidation numbers from a formula and net charge using standard classroom rules and charge balance.
This calculator is intentionally conservative. It flags ambiguous cases and should be manually checked for peroxides, superoxides, coordination compounds, and advanced redox examples.
Oxidation number estimate
Mn is estimated as +7.
| Element | Oxidation number | Rule |
|---|---|---|
| Mn | +7 | Solved by charge balance: total oxidation numbers must equal -1. |
| O | -2 | Oxygen is normally -2 outside peroxides and superoxides. |
This tool uses common classroom rules and still needs human review for peroxides, superoxides, organometallics, and advanced coordination compounds.
Use the net charge
The sum of oxidation numbers equals the charge of the compound or ion. Neutral compounds sum to zero.
Check exceptions
Peroxides, superoxides, hydrides, and coordination compounds need manual review.