Three inputs (hectares, dominant habitat, distinctiveness) return a three-route cost ceiling for the 10% net-gain obligation: on-site delivery, off-site units, statutory credits. No signup; calculator math is open-source.
Auto-resolved from the JP039 habitat lookup; editable to model alternative classifications. [S1]
Includes the 30-yr management liability. Difficulty + temporal multipliers applied to the 5-yr target. [S1]
Feb 2026 Biodiversity Units UK market report; spatial risk and trading rules apply. [S8]
Deliberately punitive last-resort. Required only where the trading rules cannot otherwise be satisfied. [S3]
This is a feasibility calculator: it reproduces the JP039 v4.0 core arithmetic in plain TypeScript. It does NOT replace the bound Defra spreadsheet at planning submission; appoint a CIEEM-registered ecologist for the formal output.
A BNG calculator sizes the biodiversity unit delta a development must deliver to satisfy the statutory 10% net-gain requirement under the Environment Act 2021. The Statutory Biodiversity Metric v4.0 (JP039) multiplies distinctiveness, condition, area, and strategic significance to produce baseline biodiversity units. Required delta = baseline x 1.10 minus post-development units. Three delivery routes are priced: on-site, off-site units, or Defra statutory credits. [S1]
Most SERP competitors return a single GBP estimate. The buyer’s actual decision is a routing problem; can the delta be delivered on the development parcel, bought as registered off-site units in the same Local Planning Authority, or forced to statutory credits as the punitive backstop. This calculator surfaces all three from the same input set so the viability appraisal can compare them like-for-like.[S2]
Statutory credits are deliberately priced above market by the Spatial Risk Multiplier (SRM) doubling rule; a Tier A1 credit at £42,000 becomes an effective £84,000 floor per unit.[S3] Off-site units from registered habitat banks typically clear at £20,000 to £50,000 per unit for medium distinctiveness, rising sharply for high and very-high.[S8]