BNG Pre-Feasibility Calculator

Site Information

Basic details used to contextualise your BNG calculation.

📍Site Details

Development Name

Site Postcode

Total Site Area (ha)Full application boundary

Development Type

Local Planning Authority

Strategic Significance Check your LPA's local nature recovery strategy

Existing Site Habitats

Map what's currently on site. Use UKHab classification — your Phase 1 survey will have these. Add area habitats and any hedgerows separately.

🌿Area Habitats — Baseline

Habitat Type	Condition	Area (ha)	BU

⚠️ One or more selected habitats may be irreplaceable — losses cannot be offset through standard BNG credits. Flag this with your ecologist and LPA immediately.

Area Habitat Baseline BU:0.00

🌳Hedgerows — Baseline

Hedgerow biodiversity units are calculated per linear kilometre. Include all hedgerows within the application boundary.

Hedgerow Type	Condition	Length (km)	BU

Hedgerow Baseline BU:0.00

ℹ️

Watercourses are also assessed in the full statutory metric (measured in km). For this pre-feasibility tool, add their riparian habitats as area types above. Watercourse-specific calculations require the full statutory metric workbook.

Proposed Development Scheme

Habitats lost to development, and new habitats you'll create or enhance on-site.

🏗️Area Habitats Lost

Habitats permanently removed or sealed within the development footprint.

Habitat Type	Condition	Area (ha)	BU Lost

⚠️ Irreplaceable habitat selected. Losses to these habitats are a potential red flag for your planning application — consult your ecologist before proceeding.

Area Habitat Lost BU:0.00

✂️Hedgerows Lost

Hedgerow Type	Condition	Length (km)	BU Lost

Hedgerow Lost BU:0.00

🌱New Area Habitats Created On-Site

New habitats within the scheme — wildflower meadow, SuDS, woodland planting, etc. Enter target condition and delivery timeframe. Connectivity reflects how well-connected to existing ecological networks.

Habitat Type	Target Condition	Area (ha)	Delivery	Connectivity	BU Created

Created Area Habitat BU:0.00

🌾New Hedgerows Created On-Site

Hedgerow Type	Target Condition	Length (km)	Delivery	Connectivity	BU Created

Created Hedgerow BU:0.00

BNG Pre-Feasibility Results

Based on Statutory Biodiversity Metric v1.0.4. For planning submissions, a full assessment by a qualified ecologist is required.

Baseline BU
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biodiversity units

Post-Dev BU

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biodiversity units

Net Gain

—

% (target ≥10%)

Off-Site Need

—

biodiversity units

Net Gain Progress0%

10% target

💰Indicative Off-Site Credit Cost

Off-site habitat credits range from ~£8k–£20k per unit (statutory credit scheme / private habitat banks). Hedgerow credits are assessed separately.

Low (£8k/unit)

—

Mid (£14k/unit)

—

High (£20k/unit)

—

📊Full Unit Breakdown

Habitat / Hedgerow	Area / Length	Condition	Distinctiveness	Multipliers	BU

Get your full BNG assessment

A full statutory assessment requires Phase 1 and Phase 2 habitat surveys, condition assessments for each parcel, and a completed statutory metric workbook. Aegaea's ecologists can take this from pre-feasibility to planning submission.

✅

Request received

Our ecologists will review your site and be in touch within one business day.

Methodology: Natural England Statutory Biodiversity Metric v1.0.4 (July 2025). Formula: BU = area/length × distinctiveness × condition × strategic significance × connectivity × temporal risk × creation risk. Condition scores: Good=1.0, Fairly Good=0.8, Moderate=0.6, Fairly Poor=0.4, Poor=0.2, N/A=1.0. Strategic significance: Low×1.0, Medium×1.10, High×1.15. Connectivity: High×1.15, Medium×1.10, Low×1.0. Temporal: 3.5%/yr compound discount (year 0=1.0, 2=0.931, 5=0.837, 10=0.700). Hedgerow BU uses per-km calculation. Watercourse habitats not separately assessed. Pre-feasibility only — not a statutory BNG assessment.