Estimate how Biodiversity Net Gain could affect developable land area, site layout and housing yield. This tool helps you test whether enough land appears to remain for onsite habitat, landscaping and green space before you rely on a tight development layout.
This calculator is for early site layout guidance only. BNG rules are changing during 2026, so always check current GOV.UK guidance, your local planning authority and ecological advice before relying on a site layout.
BNG is not just a cost issue. It can also affect how much land remains available for homes, roads, parking, gardens, open space and habitat creation. A scheme that looks viable on density may become tight once green infrastructure and habitat delivery are considered.
This calculator gives a practical first-pass view of site land take. It does not calculate official biodiversity units and does not replace the statutory biodiversity metric.
Enter broad site layout assumptions below. The result updates automatically and gives a site pressure score.
This table shows where the site area is being used and whether the layout appears to leave enough green / habitat space to explore onsite BNG.
| Land use item | Area | % of site | Comment |
|---|---|---|---|
| Building footprints | — | — | Estimated ground floor building footprint. |
| Roads, parking and turning | — | — | Hard infrastructure pressure. |
| Other hardstanding / paths | — | — | Other non-habitat land take. |
| Private gardens / amenity | — | — | Useful amenity space, but not automatically full BNG delivery. |
| Public open space / landscape buffer | — | — | Potential green infrastructure opportunity. |
| Existing habitat retained | — | — | Retained habitat may reduce pressure if it is suitable and protected. |
| New habitat / BNG creation allowance | — | — | Possible onsite BNG / green infrastructure land. |
| Unallocated / flexibility area | — | — | Remaining site flexibility after broad allowances. |
BNG can compete with roads, parking, gardens, drainage and developable land. This is especially important on small or tightly planned sites.
Onsite habitat creation usually needs real space. If the site is already dominated by homes, access and parking, BNG may become harder to deliver onsite.
If more land is needed for habitat, buffers or open space, the scheme may need fewer dwellings, smaller plots or a different layout.
If onsite delivery is unrealistic, the scheme may need off-site biodiversity units or other routes, which should be tested in the development appraisal.
Use these calculators together to check whether BNG affects site layout, cost, feasibility and planning risk.
Check whether BNG may apply, whether an exemption may be relevant and what evidence may be needed before planning.
Estimate survey costs, onsite works, off-site unit risk, management allowance and development viability impact.
Browse the full development hub for site yield, density, GDV, feasibility and planning risk calculators.
Estimate possible housing numbers from land size, density and site constraints.
Calculate dwellings per hectare and test broad housing density assumptions.
Test development costs, GDV, land value and margin assumptions before moving ahead.
Answers to common questions about BNG, developable area, green space and site layout pressure.
No. This is a land take and layout pressure calculator. It does not calculate official biodiversity units and does not replace the statutory biodiversity metric, ecology input or local planning authority requirements.
BNG can require habitat retention, habitat creation, landscape buffers, SuDS planting or green infrastructure. That land may compete with buildings, access roads, parking, gardens and other parts of the layout.
Private gardens may have some biodiversity value depending on the metric and design, but they should not be assumed to deliver the same value as planned, secured and managed habitat areas.
A tight site is one where buildings, roads, parking and hardstanding take up so much of the site that there is limited realistic space left for habitat retention or creation.
Sometimes. If a site needs more land for habitat, buffers or green infrastructure, the final layout may need fewer dwellings, smaller plots or a different access and parking arrangement.
BNG rules are changing during 2026 and a new 0.2ha area-based exemption has been announced, subject to implementation. You should check the latest GOV.UK and local planning authority guidance before relying on an exemption.
If onsite BNG delivery is not realistic, the scheme may need off-site biodiversity units or another delivery route. That should be tested early because it may affect project costs and viability.
Check it before agreeing land value or finalising the layout. BNG land pressure discovered late can affect density, cost, planning risk and development margin.
This calculator helps you spot whether BNG might create land pressure before the layout becomes fixed. Use the result alongside your housing yield, density, BNG cost and feasibility checks before relying on a scheme.
