Biodiversity Net Gain Calculator

Enter your pre-development habitat details — including habitat type, area (hectares), habitat condition, and strategic significance — to calculate your baseline biodiversity units and the post-development units required to meet the UK mandatory 10% Biodiversity Net Gain requirement. The Biodiversity Net Gain Calculator shows you your baseline units, the minimum units needed after development, and the biodiversity units deficit or surplus you need to address in your planning application.

Select the dominant habitat type on your site before development.

ha

Total area of the habitat in hectares.

Assessed condition of the habitat using standard UK field criteria.

Significance multiplier based on proximity to nature recovery networks.

Distinctiveness score reflects how rare or ecologically valuable the habitat type is.

ha

How much of the habitat area will be removed or built upon.

Expected condition of any habitat retained or newly created after development.

%

Mandatory minimum is 10% under the Environment Act 2021. Some LPAs require higher.

Results

Biodiversity Units Required (Post-Dev)

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Baseline Biodiversity Units

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Units Lost to Development

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Units Retained After Development

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Units Deficit to Offset

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Current BNG Achievement

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Biodiversity Unit Breakdown

Frequently Asked Questions

What is Biodiversity Net Gain (BNG) and when does it apply?

Biodiversity Net Gain is a legal requirement under the Environment Act 2021, meaning new developments in England must deliver a measurable 10% improvement in biodiversity compared to the pre-development baseline. As of 2nd April 2024, it applies to most planning applications, including small sites from April 2024 onwards. Developers must demonstrate this through the statutory biodiversity metric.

What are biodiversity units and how are they calculated?

Biodiversity units are a standardised measure of habitat value calculated using the statutory biodiversity metric. They are derived by multiplying a habitat's area (in hectares) by its distinctiveness score, condition score, and strategic significance multiplier. The resulting number represents the ecological value of the habitat both before and after development.

What is the statutory biodiversity metric?

The statutory biodiversity metric is the official tool published by DEFRA and Natural England for measuring biodiversity value in the context of BNG. It assesses habitats based on type, area, condition, and strategic significance to produce a biodiversity unit value. All planning applications subject to BNG must use this metric.

Who needs to use a BNG calculator?

Developers, architects, land managers, and ecologists involved in UK planning applications must calculate BNG to demonstrate compliance. Local Planning Authorities (LPAs) also use the metric to assess whether applications meet the mandatory 10% net gain requirement. Landowners looking to sell biodiversity credits also need to quantify the units their land can generate.

What happens if my development cannot achieve 10% BNG on-site?

If on-site habitat creation or enhancement cannot deliver the full 10% net gain, developers can use off-site habitat enhancements — either on land they own nearby or by purchasing statutory biodiversity credits from the government. The preference under the BNG hierarchy is always on-site delivery first, then off-site, with statutory credits as a last resort.

Are any developments exempt from the BNG requirement?

Yes, certain developments are exempt, including householder applications, self-build homes under a certain threshold, temporary developments (under 5 years), developments impacting less than 25 square metres of habitat or 5 metres of linear habitat, and urgent Crown development. You should check the full exemption criteria on the GOV.UK BNG guidance pages.

What is a Biodiversity Gain Plan and when must it be submitted?

A Biodiversity Gain Plan is a document submitted to the Local Planning Authority confirming how the 10% BNG target will be met. It includes the completed biodiversity metric, habitat management plans, and evidence of any off-site or credit arrangements. It must be approved by the LPA before development begins, typically as a pre-commencement planning condition.

What is strategic significance in the biodiversity metric?

Strategic significance is a multiplier in the statutory biodiversity metric that reflects how important a habitat is within the wider nature recovery network. Habitats located within or adjacent to Local Nature Recovery Strategy areas or the Nature Recovery Network receive a higher multiplier (up to 1.25), increasing their biodiversity unit value and making them more valuable for BNG purposes.

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