Estimate the possible cost of Biodiversity Net Gain for a development before planning. This tool helps you allow for survey costs, onsite habitat works, off-site unit risk, legal and admin costs, 30-year management and the likely effect on development viability.
BNG costs vary by habitat, location, delivery route and legal structure. This estimator is designed for feasibility planning and should not replace ecological advice, statutory metric calculations or local planning authority requirements.
The hidden cost of Biodiversity Net Gain is not just the survey. A development may also need habitat design, onsite enhancement, off-site units, legal agreements, monitoring and long-term management.
This estimator helps you create a sensible BNG provision before agreeing a land value, finalising a small-site feasibility appraisal or moving into planning.
Enter your assumptions below. The result updates automatically and shows low, likely and high BNG cost provisions for early development planning.
The table below separates professional costs, onsite works, long-term management, off-site unit risk and contingency.
| Cost item | Low | Likely | High | Risk type |
|---|---|---|---|---|
| Survey, reporting and metric allowance | — | — | — | Professional |
| Legal / S106 / admin allowance | — | — | — | Planning |
| Onsite habitat works | — | — | — | Variable |
| 30-year management allowance | — | — | — | Long-term |
| Off-site unit risk | — | — | — | Market / site risk |
| Contingency | — | — | — | Buffer |
| Total BNG provision | — | — | — | Estimated |
The biggest risk is usually not just the survey. Costs can change sharply when the scheme cannot deliver enough biodiversity onsite or needs long-term habitat management.
A straightforward site may only need limited evidence, but habitat uncertainty can push a project toward a fuller metric, habitat condition assessment or ecological appraisal.
If BNG can be delivered onsite, the cost may be easier to control. Tight sites with limited green space are more exposed to off-site unit pricing.
BNG may create ongoing management and monitoring responsibilities. That can become a real development cost even after the planning work is complete.
Use these tools alongside the estimator to test planning risk, site yield, GDV and wider development feasibility.
Check whether BNG may apply, whether an exemption may be relevant and what evidence may be needed before planning.
Browse the full land development hub for housing yield, GDV, planning risk and feasibility calculators.
Test development costs, GDV, land value and margin assumptions before moving ahead.
Estimate gross development value before testing costs, planning risk and margin.
Check common planning risk factors before spending heavily on a site.
Estimate possible housing numbers from land size, density and site constraints.
Answers to common questions about Biodiversity Net Gain costs, off-site units, statutory credits and development viability.
No. This is a feasibility estimator. It does not calculate official biodiversity units and does not replace the statutory biodiversity metric or ecological advice.
BNG delivery can involve long-term habitat management and monitoring. This can become a real project cost, especially where significant onsite or off-site habitat is used to deliver the gain.
No. Off-site BNG unit prices vary by habitat type, geography, availability and legal arrangements. The unit price in this calculator is editable so you can test different assumptions.
No. Statutory biodiversity credits are a last-resort government route where onsite and off-site options cannot deliver the required BNG. They should not be treated as normal market unit prices.
Use the result as an early cost provision when testing site feasibility, land value or development margin. If the result shows medium, high or severe risk, get site-specific ecological and planning advice before committing to the scheme.
BNG can affect viability because it may add professional fees, habitat works, long-term management costs, legal agreements and possible off-site unit costs. On tight-margin sites, these costs can reduce the amount a developer can afford to pay for land.
Sometimes. Keeping existing habitat, reducing habitat loss, creating useful onsite habitat and designing green space earlier in the scheme can reduce the risk of relying on off-site units or more expensive solutions later.
Yes. BNG should be considered before agreeing a land price, especially on greenfield, garden, scrub, woodland, watercourse or habitat-rich sites. A late BNG cost can reduce profit, change the layout or affect whether the site remains viable.
BNG can affect both planning risk and land value. Use this estimate as an early allowance, then test the site properly with the statutory metric, ecological advice and your local planning authority’s requirements before relying on the figures.
