The Statutory Biodiversity Metric

The Statutory Biodiversity Metric provides tools and guides for measuring the biodiversity value of a habitat. Its primary purpose is supporting Biodiversity Net Gain (BNG) in England.

The tools allows the calculation of biodiversity value for the purpose of BNG for developments. For BNG, biodiversity is measured in standardised units; the Statutory Biodiversity Metric measures the biodiversity value of habitats by calculating the number of biodiversity units. It calculates how many units a habitat contains before developments take place and how many units are needed to achieve the 10% BNG requirement for England.

Guidance for the Metric is designed to support ‘competent’ assessors and reviewers using the Statutory Biodiversity Metric calculation tool. The BNG requirement comes into effect at different times, depending on the size of the development. This includes ‘major developments’ and ‘small developments’, alongside ‘nationally significant infrastructure projects’ from late November 2025. For Small Sites as defined by the Town and Country Planning Order 2015, the simpler Metric is also available.

Defra published the Metric in November 2023. This builds on previous versions of the biodiversity metric developed collaboratively with Natural England, Environment Agency and the Forestry Commission.