ISO 16128 defines natural cosmetics by providing a standardized framework for calculating how “natural” a cosmetic ingredient or finished product is. It does this through a numerical index, the natural origin index, that expresses the proportion of a formula derived from natural sources. The standard does not certify products as “natural” outright; it gives brands and manufacturers a consistent, science-based method for measuring and communicating naturalness.
Developed by the International Organization for Standardization, ISO 16128 was created to bring clarity to a cosmetics market where “natural” had long been used without any agreed definition. It applies to any brand or manufacturer that wants to substantiate naturalness claims with a transparent, reproducible calculation. The sections below unpack exactly how the standard works, what it includes, and where its limits lie.
ISO 16128 measures the degree to which a cosmetic ingredient or finished formula originates from natural sources. It does not measure safety, efficacy, or sustainability. Instead, it provides a calculation methodology that produces a number between 0 and 1, where 1 means entirely natural in origin and 0 means entirely synthetic. This number is called the natural origin index.
The standard is published in two parts. The first part defines the terminology and categories used to classify ingredients. The second part explains the mathematical guidelines for calculating both ingredient-level and formula-level indices. Together, they give manufacturers a shared language and a reproducible method, so when two different labs assess the same formula, they can arrive at comparable results.
Importantly, ISO 16128 is descriptive, not prescriptive. It does not set a minimum threshold that a product must reach to be called “natural.” It simply provides the tool for calculating and communicating where a product sits on the naturalness spectrum.
Under ISO 16128, an ingredient qualifies as natural if it originates from plants, animals, microorganisms, or minerals and has not undergone chemical processing that substantially changes its molecular structure. Ingredients derived from these sources through physical, microbiological, or fermentation processes are generally considered natural in origin.
The standard also introduces the concept of “natural origin” ingredients, a broader category that includes substances derived from natural raw materials through chemical transformation. These are not considered purely natural, but they are not treated as fully synthetic either. Their natural fraction is calculated proportionally based on how much of the final molecule can be traced back to a natural source.
Water is a special case. ISO 16128 classifies water as a natural ingredient, which means it contributes positively to a formula’s natural origin index. This is worth noting because water is often the largest single component in skincare and haircare products, so its classification has a meaningful effect on the final index score.
The natural origin index for a finished formula is calculated by dividing the total mass of natural and natural-origin ingredients by the total mass of all ingredients in the formula. The result is a value between 0 and 1, often expressed as a percentage. An index of 0.95, for example, means 95% of the formula by weight derives from natural sources.
Each ingredient first receives its own natural origin index based on its molecular composition and processing history. For ingredients that are partially natural, such as chemically modified plant derivatives, only the natural fraction of their molecular weight counts toward the formula total. This makes the calculation more precise than a simple ingredient count, because it accounts for the degree of naturalness at the molecular level.
The formula-level calculation is straightforward in principle but can become complex in practice. Ingredients with multiple components, fermentation-derived actives, or complex extraction histories all require careful assessment before their index value can be assigned. This is one reason why working with an experienced formulation partner makes a real difference when brands want to calculate and verify their naturalness claims accurately.
ISO 16128 is a calculation standard, not a certification. It provides a method for quantifying naturalness but does not require third-party verification, auditing, or compliance with sourcing rules. Organic cosmetic certifications, such as COSMOS, NATRUE, or Ecocert, are independent certification schemes that set specific ingredient, sourcing, and manufacturing requirements and verify compliance through audits.
The practical differences are significant. A brand can use ISO 16128 to calculate and report its natural origin index internally without involving any certifying body. An organic certification, by contrast, requires ongoing third-party assessment, restricts which ingredients are permitted, and often mandates a minimum percentage of certified organic content alongside naturalness thresholds.
ISO 16128 and organic certifications are not mutually exclusive. Some certification schemes reference ISO 16128 definitions as part of their own criteria. A product can carry an organic certification and also report an ISO 16128 natural origin index. The two serve different purposes: one is a measurement tool, the other is a verified quality mark.
Not all natural cosmetics follow ISO 16128 because the standard is voluntary. No regulatory authority in the EU, US, or elsewhere requires brands to calculate or disclose a natural origin index. Brands can legally label products as “natural” without referencing ISO 16128 at all, which means many choose not to engage with the standard’s methodology.
There are also practical barriers. Calculating the natural origin index requires detailed compositional data for every ingredient, including information about processing methods and molecular origins. Smaller brands or those working with less transparent supply chains may not have access to that level of detail. The calculation can also be time-consuming without the right expertise in place.
Beyond logistics, some brands avoid ISO 16128 because it can produce results that are lower than consumers expect. A product marketed as “natural” might score a natural origin index of 0.70 or 0.80 once all ingredients are assessed, which is still a strong result, but may feel underwhelming to consumers who assume “natural” means close to 100%. For brands built around a strong natural identity, transparency about that number requires confidence in both the formula and the communication.
Yes, brands that want to make credible, substantiated naturalness claims should use ISO 16128 as the basis for those claims. The standard gives brands a defensible, science-based number to point to, which is far stronger than vague language like “made with natural ingredients.” As regulatory scrutiny of greenwashing increases across Europe and beyond, having a documented methodology behind any naturalness claim is increasingly important.
Using ISO 16128 also signals transparency. Consumers and retail buyers are becoming more sophisticated about ingredient sourcing, and a disclosed natural origin index, even if it is not 1.0, demonstrates that a brand is being honest about what is in its products. That honesty builds trust in a way that unqualified “natural” claims cannot.
The main caveat is that ISO 16128 should be communicated clearly and in context. Presenting a natural origin index without explanation can confuse consumers who are unfamiliar with the scale. Brands that use the standard effectively tend to pair the index with a brief explanation of what it means, making the number accessible rather than technical.
Navigating ISO 16128 is much easier when you work with a formulation partner who already understands the standard inside and out. As a natural cosmetics manufacturer, we work exclusively with natural ingredients and maintain a portfolio of over 500 carefully selected raw materials, all ethically sourced and well-documented. That means when a brand wants to calculate a natural origin index for a formula, we already have the ingredient-level data needed to do it accurately.
Here is what working with us on naturalness substantiation looks like in practice:
Whether you are developing a new product line or reviewing an existing formula, understanding how we work is a good place to start. If you are ready to talk about your specific formulation goals, get in touch with us and we will be happy to help.
Yes, and this is one of the most important limitations of ISO 16128 to understand. The standard measures origin and naturalness, not safety or skin compatibility. Some naturally derived ingredients can cause irritation, allergic reactions, or other concerns, while some synthetic ingredients are well-tolerated and thoroughly safety-tested. A high natural origin index should never be used as a proxy for product safety — those are two separate assessments governed by different frameworks.
Start by gathering the full compositional data for every ingredient in your formula, including information on how each ingredient was processed and what proportion of its molecular structure traces back to a natural source. Your ingredient suppliers should be able to provide technical data sheets or declarations that include this information. If you’re working with a formulation partner, they can often handle this assessment directly, since they typically already hold the raw material documentation needed to run the calculation accurately.
A lower-than-expected index is actually a useful diagnostic tool rather than a dead end. It tells you exactly which ingredients are pulling the score down, giving you a clear starting point for reformulation. In many cases, swapping one or two key synthetic ingredients for natural-origin alternatives can meaningfully improve the index without compromising the product’s performance or stability. Working with a formulation partner who has a broad natural ingredient portfolio makes this kind of targeted reformulation much more practical.
The calculation methodology in ISO 16128 applies the same way regardless of product type — it is based on the weight proportion of natural and natural-origin ingredients in the formula, whether the product is rinsed off or left on the skin. However, the ingredient composition of rinse-off products often differs significantly from leave-on products, which can affect the index score in practice. For example, rinse-off products typically contain higher water concentrations and different functional ingredients, both of which influence the final natural origin index.
ISO 16128 itself does not set a minimum threshold, so there is no universally mandated score required to use the word ‘natural.’ However, if you are pursuing a third-party organic or natural certification such as COSMOS or NATRUE, those schemes do impose specific minimum naturalness thresholds as part of their criteria. Even without certification, a higher index score — generally 0.90 and above — tends to hold up better under regulatory scrutiny and consumer expectations, particularly as greenwashing regulations tighten across Europe.
Yes, you can reference ISO 16128 in marketing materials and on product labelling, provided the natural origin index you disclose has been calculated correctly using the standard’s methodology. The key requirement is accuracy and transparency — the number you communicate must be genuinely derived from the ISO 16128 calculation, not estimated or approximated. It is also good practice to include a brief explanation of what the index means so that consumers can interpret the figure in context, rather than presenting a number without any supporting explanation.
You should recalculate the natural origin index whenever there is a change to your formula, including ingredient substitutions, supplier changes, or adjustments to ingredient concentrations. If a supplier changes their manufacturing process for a raw material, that can also affect the ingredient’s natural origin status and therefore your formula-level score. Building a habit of recalculating at every formula revision ensures that any naturalness claims you make remain accurate and defensible over time.
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