Oxide ↔ element converter
Supplier certificates report oxides. Buyer specifications are written in elements. Convert either way, check the result against your limit, and see the factor derived from the atomic masses it comes from.
The figure as it appears on the certificate. A mass ratio, so the unit carries through unchanged.
Read on the element basis, which is how a buyer specification is written. Leave blank to convert without a verdict.
- Fe₂O₃ as reported
- 0.07%
- Fe equivalent
- 0.049%
Value × 0.6994. The factor is the element’s share of the oxide’s formula mass — derived below, not stored.
Against your limit
Passes
Fe 0.049% against a limit of 0.05%.
Writing the limit against Fe₂O₃ when you mean Fe over-specifies by about 30%. A limit of 0.05% on the Fe₂O₃ basis is a requirement of 0.035% on the Fe basis. The material has to be that much cleaner, and you pay for headroom you never asked for. The same mismatch read the other way lets a compliant lot look like a failure: check which basis a certificate uses before rejecting it.
Paste-ready specification line
States the requirement on the element basis and the oxide equivalent alongside it, so a supplier can check it against a COA without converting anything — which is what stops the mismatch recurring.
Fe ≤ 0.05% (elemental basis — equivalent to Fe₂O₃ ≤ 0.0715%, factor 0.6994)The worked example
A COA reporting Fe₂O₃ 0.07% satisfies an “Fe ≤ 0.05%” specification, because it is Fe 0.049%. Written the other way round — “Fe₂O₃ ≤ 0.05%” when Fe ≤ 0.05% was meant — the same specification tightens to Fe 0.035%. Load either direction:
How the factor is derived
Each factor is the element’s share of the oxide’s formula mass, computed from standard atomic weights every time this page renders. None is stored as a decimal, so none can drift from the masses it came from.
factor = (n × M_element) / (n × M_element + m × M_oxygen)| Conversion | Element mass (u) | Oxygen mass (u) | Formula mass (u) | Factor |
|---|---|---|---|---|
| Fe₂O₃ → Fe | 2 × 55.845 = 111.690 | 3 × 15.999 = 47.997 | 159.687 | 0.6994 |
| Sc₂O₃ → Sc | 2 × 44.955908 = 89.912 | 3 × 15.999 = 47.997 | 137.909 | 0.6520 |
| Y₂O₃ → Y | 2 × 88.90584 = 177.812 | 3 × 15.999 = 47.997 | 225.809 | 0.7874 |
| TiO₂ → Ti | 1 × 47.867 = 47.867 | 2 × 15.999 = 31.998 | 79.865 | 0.5993 |
| SiO₂ → Si | 1 × 28.085 = 28.085 | 2 × 15.999 = 31.998 | 60.083 | 0.4674 |
Standard atomic weights as published by IUPAC/CIAAW (2021 table). The quoted uncertainty on each weight is orders of magnitude below the precision any certificate of analysis is written to.