This part of EN 16785 specifies a method of determining the bio-based content in products using the material balance applied to a representative product batch in a production unit. This European Standard is applicable to any solid, liquid and gaseous bio-based product containing carbon, obtained by chemical synthesis, mixing or assembling, provided that: for a product batch, the composition of the product and the bio-based content of each input and loss in the production unit are known, and the bio-based content of the product is verifiable by analysis. This method is not needed for the determination of the bio-based content in natural products wholly derived from biomass. Annex A gives examples of determination of the bio-based content according this method.