Calculating the RLI


The RLI value is calculated by multiplying the number of species in each red list category by the category weight (0 for LC, 1 for NT, 2 for VU, 3 for EN, 4 for CR and 5 for EX) these products are summed, divided by the maximum possible product (number of species multiplied by the maximum weight of 5) and subtracted from one (Bubb et al. 2009) This produces an index value that ranges from 0 to 1.

RLI calculation



For guidelines on the national use of the Red List Index, and calculation tools to assist in the production of the index, see:

The IUCN Red List website

IUCN Red List Index – Guidance for National and Regional Use

Red List Index calculator, downloadable from the Biodiversity Indicators Partnership website and the IUCN Red List website