Guide
BNG metric calculation: how the 10% gain is measured, and the cost
Updated
A BNG metric calculation scores the habitats on a site before development and after it, and shows whether the result beats the starting value by at least 10%. Ecologists publish prices for the work from £295 to £589.
What the metric measures
The objective is met if the post-development biodiversity value exceeds the pre-development value by at least 10% (GOV.UK planning guidance). Unless a development is exempt, the 10% applies to all habitats within the red line, whether or not they are affected (GOV.UK, understanding biodiversity net gain).
Which tool
GOV.UK publishes the statutory biodiversity metric and the small sites metric, with their user guides (statutory metric tools and guides). The calculation is only as good as the habitat survey behind it, which is why most firms price the survey and the metric together.
What it costs
| Consultancy | What it publishes | Price |
|---|---|---|
| Talk-Ecology | PEA and BNG | from £295 |
| ACP Consultants | straightforward BNG survey | from £399 + VAT |
| Arbtech | biodiversity net gain plan | from £489 |
| Joe's Blooms | BNG metric, standard application | £495, up to £995 for complex sites |
| Aware Ecology | BNG surveys | from £499 + VAT |
| Biodiversity Net Gain Plan | rapid assessments and net gain plans | from £589 + VAT |
Sources: Talk-Ecology, ACP Consultants, Arbtech, Joe’s Blooms, Aware Ecology and Biodiversity Net Gain Plan, each on its own page (every row, with its source).
If the site cannot reach 10%
Developers who cannot reach the gain on site can buy off-site units, and as a last resort statutory biodiversity credits from the government; an application for credits can take up to 8 weeks to approve (GOV.UK, statutory biodiversity credits). Registering an off-site gain site costs £639 (GOV.UK, register a biodiversity gain site).
Published figures are what each consultancy advertises on its own page, read through our fetch box on the date shown. A 'from' price is the firm's floor, not the price of your assessment.