Odor Concentration Calculator
Turn a dilution-to-threshold ratio into an odour concentration in ouE/m³ — the core quantity that EN 13725 dynamic olfactometry measures.
Odour concentration
By the EN 13725 definition, a sample’s odour concentration in European odour units per cubic metre (ouE/m³) equals the dilution factor that brings it to its detection threshold, so the two numbers are the same. Concentrations span orders of magnitude, which is why the log₁₀ value is shown too.
What odour concentration actually means
Odour concentration is not a chemical measurement — it is a sensory one. Rather than counting molecules, olfactometry asks how much a sample must be diluted before a trained panel can only just detect it. The dilution factor at that 50% detection threshold is the odour concentration, reported in European odour units per cubic metre. It lets wildly different odour mixtures be compared on a single scale.
That is why this tool is deliberately simple: once you know the dilution-to-threshold ratio, the odour concentration is the same number. What the calculator adds is the log₁₀ view and a rough strength band, so you can place a result in context before it feeds an emission-rate or dispersion calculation.
Frequently Asked Questions
What is an odour unit (ouE)?
One European odour unit (ouE) is the amount of odorant that, dispersed in one cubic metre of neutral gas at standard conditions, sits right at the detection threshold of an average panel — the point where 50% of assessors just detect an odour. Odour concentration is then expressed in ouE per cubic metre (ouE/m³).
How does the dilution-to-threshold ratio give a concentration?
In dynamic olfactometry a sample is progressively diluted with clean air until the panel can only just detect it. The dilution factor at that 50% threshold is, by definition, the sample's odour concentration in ouE/m³. So a sample that has to be diluted 1000-fold to reach threshold has an odour concentration of 1000 ouE/m³.
Why does the tool show a log10 value?
Odour concentrations range across several orders of magnitude — from a few ouE/m³ near a threshold to hundreds of thousands at a strong source. Working in log10 keeps those figures manageable and matches how olfactometry data are usually averaged and reported.
Is a higher number worse?
A higher odour concentration means a more concentrated odour at the point of sampling, but nuisance depends on far more — emission rate, dispersion, weather, distance to people, and how offensive the odour is. Concentration is one input to that picture, not the whole answer.
Does this replace laboratory olfactometry?
No. A defensible odour concentration comes from an accredited laboratory running a panel on a calibrated olfactometer under EN 13725, with quality controls this simple converter can't reproduce. Use this to understand and sanity-check the relationship, not to certify a result.
Screening estimates only — not a substitute for accredited EN 13725 olfactometry, dispersion modelling, or regulatory advice.