Product Category Rules (PCR) are documents that provide rules, requirements, and guidelines for developing an EPD for a specific product category. They are used as complements to the programme instructions, e.g. in terms of calculation rules, scenarios, and EPD contents. A PCR should enable different practitioners using the PCR to generate consistent results when assessing products of the same product category. About 100 PCRs are already available in the PCR library. A new PCR may be developed if there is none for a product category.