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Biodiversity net gain

What biodiversity net gain is, land manager guidance, developer guides and how to calculate biodiversity value.

Biodiversity net gain (BNG) is a way to contribute to the recovery of nature while developing land. It is making sure the habitat for wildlife is in a better state than it was before development.

From 12 February 2024 Major Planning Applications (as defined by The Town and Country Planning Act 1990) and from 2 April Minor Planning Applications are subject to biodiversity net gain legalisation. All applications, unless exempt, must be submitted with the statutory biodiversity metric tool.

Developers must deliver a BNG of 10%. This means a development will result in more or better quality natural habitat than there was before development.


Measuring biodiversity  

For the purposes of BNG, biodiversity is measured in standardised biodiversity units. 

A habitat will contain a number of biodiversity units, depending on things like its:  

  • size  
  • quality  
  • location   
  • type

Biodiversity units can be lost through development or generated through work to create and enhance habitats. 

Calculating the units

There is a statutory (official) biodiversity metric, which is a way of measuring:

  • how many units a habitat contains before development  
  • how many units are needed to replace the units of habitat lost and to achieve 10% BNG

Using the statutory biodiversity metric tool

To prove you have accurately calculated the number of biodiversity units for existing habitat, or habitat enhancements to achieve BNG, you must use the calculator called the statutory biodiversity metric tool on GOV.UK.

This tool applies the statutory biodiversity metric formula. 

Read the GOV.UK guidance on the biodiversity metric.

Who BNG rules will affect 

You need to know about the new rules if you're a: 

  • developer of: 

    • major developments from 12 February 2024  
    • small sites from 2 April 2024    
    • nationally significant infrastructure projects from late November 2025   
  • land manager wanting to sell in the BNG market 
  • local planning authority (LPA

Exempt developments 

Some developments are exempt from BNG regulations. 

Find out what types of development are exempt on GOV.UK.


The government has published more information about BNG in:

Local guidance

The Essex Local Nature Partnership has produced some local guidance on BNG