The natural-origin percentage in cosmetics is calculated using ISO 16128, an internationally recognised standard that defines how to determine the natural origin index of cosmetic ingredients and finished products. Each ingredient receives a score between 0 and 1 based on how much of it comes from a natural source, and those scores are combined into a single percentage for the final formula. This calculation applies to any cosmetic product making a natural origin claim, and the sections below unpack exactly how it works in practice.
The natural-origin percentage in cosmetics is calculated according to ISO 16128, a two-part international standard published by the International Organization for Standardization. Part 1 defines the terms and criteria for classifying ingredients, while Part 2 provides the actual calculation method for determining the natural origin index of both individual ingredients and finished products.
ISO 16128 was developed specifically to bring consistency to an industry where terms like “natural” had no agreed scientific definition. Before this standard, brands could make natural claims with little accountability. ISO 16128 gives cosmetic manufacturers, formulators, and certifiers a shared framework for calculating and communicating natural origin content in a transparent and reproducible way.
It is worth noting that ISO 16128 is a calculation standard, not a certification. It does not prohibit synthetic ingredients or require a minimum natural-origin score. It simply defines how to measure and express what is in a formula.
Under ISO 16128, cosmetic ingredients are classified into four categories based on their origin and the degree of processing they have undergone. An ingredient is considered fully natural if it comes directly from a plant, animal, mineral, or microbial source with minimal processing. Ingredients derived from natural sources but processed more extensively are classified as natural-origin ingredients.
The four categories are:
The classification determines the natural origin index assigned to each ingredient, which is a value between 0 (fully synthetic) and 1 (fully natural). Ingredients that are partially derived from natural sources receive a fractional score reflecting the proportion of their molecular structure that originates from nature.
The natural origin index of a finished product is calculated by multiplying each ingredient’s natural origin index by its weight percentage in the formula, summing all those values, and dividing by the total weight of the formula. The result is expressed as a percentage. In simple terms, it is a weighted average of the natural origin scores of every ingredient in the product.
For example, if a formula contains 70% water (natural origin index of 1), 20% of a natural-origin emollient with an index of 0.8, and 10% of a synthetic preservative with an index of 0, the calculation would be:
This means that even a small amount of a highly synthetic ingredient can lower the overall score significantly, while a formula built primarily on water and plant-based actives can achieve a very high natural origin index even if it contains trace amounts of processed or synthetic components.
A product can claim 99% natural origin and still contain synthetic ingredients because the ISO 16128 natural origin index is a weighted calculation, not a binary filter. If a synthetic ingredient is present in a very small quantity, its contribution to the overall index is proportionally tiny. The remaining 99% of the formula, by weight, may consist entirely of natural or natural-origin ingredients with high index scores.
This is not a loophole or a misleading practice. It reflects the mathematical reality of how formulas are built. Many cosmetic products require small amounts of synthetic preservatives, chelating agents, or stabilisers to remain safe and effective on the shelf. If those ingredients make up just 0.5% of the formula, their impact on the natural origin index is minimal, and the product can still legitimately achieve a very high natural origin score.
This is why understanding the calculation method matters as much as reading the final percentage. A 99% natural origin claim is meaningful when it is calculated transparently using ISO 16128, and less meaningful when it is not based on any standardised method at all.
The difference between “natural” and “natural-origin” on a cosmetic label is significant. Natural refers to ingredients that are taken directly from nature with minimal processing, such as cold-pressed oils or mineral clays. Natural-origin refers to ingredients that start from a natural raw material but undergo chemical transformation to produce a new molecule, such as a plant-derived surfactant or emulsifier.
Under ISO 16128, both categories contribute to the natural origin index, but they are not equivalent. A natural ingredient scores a full 1, while a natural-origin ingredient may score anywhere between 0 and 1 depending on how much of its final molecular structure traces back to a natural source.
On product labels and marketing materials, brands sometimes use “natural” and “natural-origin” interchangeably, which can mislead consumers. A product labelled as “natural” may in fact contain many natural-origin ingredients that have been chemically modified. When evaluating a product’s credentials, it is more informative to look for the ISO 16128 natural origin index alongside the ingredient list rather than relying on label language alone.
Yes, the natural-origin percentage has real limits. It tells you what proportion of a formula, by weight, derives from natural sources. It does not tell you whether those ingredients are sustainably sourced, ethically produced, biodegradable, safe for sensitive skin, or free from harmful processing by-products. A high natural origin index is one signal of a product’s composition, not a complete picture of its quality or environmental impact.
Some important things the natural-origin percentage does not capture include:
This is why the natural-origin percentage is best understood as one data point within a broader evaluation of a product’s formulation, ingredient sourcing, and sustainability credentials. It is a useful and standardised metric, but it works best when paired with transparency about where ingredients come from and how they are processed.
At Rebel Nature, we specialise in developing and manufacturing 100% natural cosmetic products for brands that care about what goes into their formulas. Understanding the natural-origin percentage is not just a technical exercise for us. It is central to how we formulate every product we create.
Here is what working with us on natural-origin formulation looks like in practice:
If you want to develop a product with a strong, verifiable natural-origin story, we would love to help. Get in touch with us to start the conversation, or learn more about how we work with brands from concept to finished product.
The core calculation behind ISO 16128 is straightforward enough to perform manually in a spreadsheet: multiply each ingredient’s natural origin index by its weight percentage, sum the results, and divide by 100. The more complex part is accurately assigning the correct natural origin index to each ingredient, which requires access to supplier documentation, technical data sheets, and a solid understanding of the standard’s classification criteria. Many formulators and contract manufacturers use dedicated formulation software that incorporates ISO 16128 indices, but working with an experienced formulation partner is often the most reliable way to ensure accuracy, especially for novel or complex ingredients.
The natural origin index for each ingredient should be provided by your raw material supplier in the form of a technical data sheet or a dedicated ISO 16128 declaration. Reputable ingredient suppliers typically include this information as standard, particularly those supplying to natural and organic cosmetic brands. If a supplier cannot provide this data, you or your formulator may need to calculate the index from first principles using the ingredient’s known molecular structure and the classification rules set out in ISO 16128 Part 1 — which is why working with suppliers who are transparent about their ingredient origin is so important.
Not necessarily. A high natural-origin index tells you about the source of the ingredients by weight, but it says nothing about efficacy, safety, allergen potential, or sustainability. Some of the most potent skin irritants and allergens — such as certain essential oils and botanical extracts — are fully natural and would score a 1 under ISO 16128. Conversely, some carefully selected synthetic ingredients at trace levels can improve product safety and shelf stability. The natural-origin percentage is a valuable formulation metric, but it should always be evaluated alongside a full ingredient assessment, dermatological testing, and sourcing transparency.
ISO 16128 is a calculation standard that provides a methodology for measuring and expressing natural origin content — it does not certify products or set minimum thresholds. Certification schemes like COSMOS (which includes Ecocert and BDIH) and NATRUE, on the other hand, are third-party programmes that set their own eligibility criteria, permitted ingredient lists, sourcing requirements, and minimum natural or organic content thresholds, and they require independent auditing and verification. Many certified natural and organic products use ISO 16128 as part of their compliance framework, but achieving a high ISO 16128 index alone does not mean a product qualifies for any certification. If certification is your goal, you need to meet the specific requirements of the relevant scheme.
This is a common and fair concern. Because water is assigned a natural origin index of 1 under ISO 16128 and is often the largest single ingredient by weight in rinse-off and water-based products, it does contribute significantly to the overall natural origin score. A product that is 70% water will start with a strong baseline before any other ingredients are considered. This is not inherently misleading — water is a natural ingredient — but it does mean that a high natural-origin percentage in a water-heavy product is not the same achievement as a high score in an anhydrous formula like a balm or oil serum. Reading the full ingredient list alongside the index gives a much more complete picture.
The most frequent mistake is using the term ‘natural’ loosely without specifying whether claims are based on ISO 16128 or any standardised method at all, which can expose brands to greenwashing accusations and regulatory scrutiny. Another common error is conflating ‘natural-origin’ with ‘organic,’ ‘non-toxic,’ or ‘hypoallergenic’ — terms that carry entirely different meanings. Brands also sometimes round up their natural-origin percentage or omit mention of the calculation standard, which undermines consumer trust. Best practice is to state the natural origin index clearly, reference ISO 16128, and avoid implying that a high score means the product is certified, allergen-free, or sustainably sourced unless those claims can be separately substantiated.
ISO 16128 is an international standard developed by the International Organization for Standardization and is recognised across many markets, including Europe, the United States, Japan, and beyond. However, it is not legally mandated in any major market — no regulation currently requires brands to use ISO 16128 specifically when making natural origin claims. Different regions may have their own guidelines or expectations around natural claims, and individual certification bodies may interpret or supplement the standard in their own ways. If you are selling across multiple markets, it is worth checking whether your target regions have any additional local requirements or preferred frameworks alongside ISO 16128.
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