Oxide Moles & Cations Calculator
Convert an oxide wt% analysis into oxide moles, cation amounts and oxygen amounts — with optional oxygen- or cation-basis normalisation — the transparent first step toward a mineral formula.
Oxide analysis (wt%)
| Oxide | wt% | |
|---|---|---|
Iron valence comes from the input oxide (FeO vs Fe₂O₃) — total Fe is not split into Fe²⁺/Fe³⁺ automatically.
Moles, cations & oxygens
Runs entirely in your browser. Your assay data is not uploaded or stored by Zerdly.
- Enter at least one valid oxide and wt%.
Assumptions & basis
- Iron valence: Taken from the input oxide (FeO vs Fe₂O₃); not split automatically (user)
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter each oxide (e.g. SiO2, FeO, MgO) with its wt%.
- Optionally choose a normalisation basis and a target number of oxygens or cations.
- Read the moles, cations and oxygens per oxide, the totals and any normalised cations.
How it works
For each oxide, the mole amount is its wt% divided by its formula mass. Multiplying by the cations and oxygens in the oxide formula gives the cation and oxygen amounts: SiO₂ contributes one Si cation and two oxygens per mole; Al₂O₃ contributes two Al and three oxygens. Formula masses are computed from the same versioned atomic-weight table used across the cluster.
Normalising to a fixed number of oxygens (or cations) scales every cation by target ÷ total, which is the standard route to atoms per formula unit. Iron valence is taken from the oxide you enter — FeO is ferrous, Fe₂O₃ is ferric — and the tool never splits a total-iron value into Fe²⁺/Fe³⁺ on its own.
Worked example
One mole of SiO₂. 60.083 wt% SiO₂ ÷ 60.083 g/mol = 1.000 mole, giving 1.000 Si cation and 2.000 oxygens. Adding more oxides and normalising to a fixed oxygen count converts the analysis toward atoms per formula unit.
Common mistakes
- Entering total Fe expecting an automatic Fe²⁺/Fe³⁺ split — choose FeO or Fe₂O₃ explicitly.
- Normalising cations without stating the oxygen basis you used.
- Mixing an oxide's cation count up (e.g. treating Al₂O₃ as one Al).
Frequently asked questions
Why normalise to oxygens?
Mineral formulae are conventionally calculated on a fixed number of oxygens (or cations) per formula unit. Normalising the cation totals to that basis is the standard route to atoms per formula unit (APFU).
How is iron handled?
By the oxide you enter: FeO is ferrous iron, Fe₂O₃ is ferric. The tool does not recast total iron into a valence split — that needs a stated method.
Related tools
- Molar Mass & Elemental Composition Calculator
- Elements to Oxide Calculator
- Mg Number (Mg#) Calculator
- Mineral Formula / APFU Calculator
- Major Oxide Normalization Calculator
- Loss on Ignition (LOI) Calculator
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Cite this tool
Zerdly. (2026). Oxide Moles & Cations Calculator. Retrieved from https://www.zerdly.com/tools/oxide-cations-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.