Converter
scaled dimension-one fraction expression · Chemistry / environment / materials · Modern widespread
parts per million
exact
- Record
- M590
- Definition quality
- Exact by definition
- Conversion mode
- contextual
- Calculator
- Context required
Definition
Parts per million means one part in one million, but the kind of 'part' must be stated or inferable from a defined quantity.
History & use
NIST/IUPAC-oriented sources prefer explicit quotient quantities and units over ambiguous 'ppm' in rigorous chemical reporting.
Modern use
Modern use is context-dependent and varies by region or measurement system.