A lake at sunset, demonstrating an example of a BNG habitat where the biodiversity value can be measured by the biodiversity metric

A Guide to the Statutory Biodiversity Metric for Developers

This guide explains how developers can use the statutory biodiversity metric to calculate their biodiversity net gain (BNG) requirements

The statutory biodiversity metric is the official government tool used to assess biodiversity value for biodiversity net gain (BNG). In simple terms, it acts as a biodiversity net gain calculator.

The metric is used to measure a wide range of habitats, including grassland, woodland, hedgerows, lakes and watercourses. It calculates the number of biodiversity units present, taking into account several factors including the habitat’s size, condition, strategic significance and type. It also considers the difficulty of creation or enhancement, and the time it takes for the habitat to mature.

The biodiversity metric is essential for helping developers to understand how many biodiversity units will be lost due to development and how many units will be required to both replace those losses and achieve the mandatory 10% BNG uplift.

Who is the tool for?

The biodiversity metric should be used for both small and major developments that are subject to mandatory BNG requirements. From May 2026, nationally significant infrastructure projects will also be required to use the metric.

For small sites that meet specific size criteria and do not contain priority habitats, developers may use the Small Sites Metric.

For major developments, the metric must be completed by a suitably qualified expert, such as an ecologist. The local planning authority (LPA) may reject the submitted calculations if a competent person has not completed them.

To calculate how a development will change the biodiversity of a habitat, an ecologist will enter any relevant information about the existing habitat and planned development into the tool.

Should you require support using the biodiversity metric, BNG Units LTD works with a trusted network of ecologists who can calculate your required BNG Units.

A pond and wildflower meadow, two example of habitats measured by the biodiversity metric — *The biodiversity metric can be used to measure the value of habitats such as grassland and lakes. The value of each would be calculated individually as they are two distinct habitats.*

What information is required to use the biodiversity metric?

Your ecologist will survey the site and gather information about each habitat parcel. A ‘habitat parcel’ is a defined area within a site that contains one type of habitat.

For each habitat parcel, the following information is required:

habitat type
habitat condition
habitat size.

Habitat size should be provided as:

hectares or square metres for area habitats, or
kilometres or miles for linear habitats, such as watercourses and hedgerows.

Your ecologist will also need to know whether the proposed actions for each habitat:

are mapped (in draft) within the Local Nature Recovery Strategies habitat map, or
are identified in alternative strategies.

For on-site calculations, it is essential that everything within the development’s red line boundary is included.

Using the biodiversity metric as a developer

The statutory biodiversity metric is a vital tool for developers as it helps assess what actions are required to achieve BNG.

If you enter the details of your development into the metric tool and find that the scheme does not deliver a 10% biodiversity net gain, you will need to revise the site design or consider off-site gains. The metric will calculate what the number and type of off-site units required.

Once you know the type and number of units required to meet your BNG requirements, BNG Units LTD will be able to work quickly to deliver your units, responsibly and reliably.

If you require assistance using the metric, contact us and we will put you in touch with a trusted local ecologist.