---
title: "Parts per million: research glossary | Sable Peptides"
description: "Parts per million (ppm) is a dimensionless ratio meaning one part in one million. In mass spectrometry, mass error is expressed in ppm by dividing the diff"
canonical: https://www.sablepeptides.co.uk/glossary/parts-per-million
publisher: Sable Peptides Limited (UK company 17488610)
note: Research use only. Not for human or veterinary use.
---

Glossary

# Parts per million

Parts per million (ppm) is a dimensionless ratio meaning one part in one million. In mass spectrometry, mass error is expressed in ppm by dividing the difference between observed and theoretical mass by the theoretical mass and multiplying by one million. It is also used for trace impurity levels.

Source: [en.wikipedia.org](https://en.wikipedia.org/wiki/Parts-per_notation)

## Related terms

-   [Mass spectrometry](/glossary/mass-spectrometry)

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