Method
How our calculators work
Every figure our calculators show comes from somewhere you can check. This page sets out where, and what we assume.
What BNG units could cost
For each line of units you need, we look at every listing published on BNG Online today and keep those that can meet it under the Trading rules
Rules on which habitat can replace which. You can replace a lost habitat with a more distinctive one (trading up) but never a less distinctive one (trading down). Higher-value habitats usually need the same type. Learn more about Trading rules and have units left. For each one we work out the Delivered cost
What units from a habitat bank really cost you once the spatial risk multiplier is applied: the units you must buy for your need, times the asking price. A cheaper price far away can cost more than a dearer one nearby. It is our estimate; your ecologist confirms the final figure. Learn more about Delivered cost: the units you would have to buy after the Spatial risk multiplier
A penalty for buying units far from the development. Same area counts in full; neighbouring areas count at 0.75; anywhere else in England at 0.5, so you must buy more units. Rules are moving towards LNRS areas. Learn more about Spatial risk multiplier (no penalty in the same planning authority or national character area, more units from a neighbouring one, twice the units from further away; watercourses by river catchment), times the asking price.
- Low is the cheapest delivered cost, high the dearest and middle the median. When some listings can supply the whole line on their own, the range covers only those, so the figures compare like with like.
- Asking prices are before any offer. Sellers may accept less; we never show their hidden reserve.
- When no listing can meet a line today, we use prices agreed in deals signed on BNG Online in the last 12 months, but only when there are at least 3, so no single deal's price is revealed. Otherwise, when at least 3 of our listings had asking prices in the last 12 months, we use those, so no single seller's price is shown on its own. These are before the spatial risk multiplier, which can mean buying up to twice the units.
- If we have none of these, we use published market prices for habitat units in England, which our team keeps up to date. We take the habitats that could meet the line at the lowest distinctiveness that can, and show the cheapest, middle and dearest price. They are market estimates, not BNG Online prices, and are before the spatial risk multiplier.
- If there is no published price either, we say so rather than guess.
- For comparison we show government Statutory biodiversity credits
Credits sold by the government as a last resort when a developer cannot find enough units. They are deliberately expensive, from about £42,000 each, with two needed per unit of shortfall, so they set a price ceiling. Learn more about Statutory biodiversity credits at the gov.uk price: 2 credits a unit at the tier the official metric gives the habitat. - If you upload a metric, we read the lines the developer still needs from its trading summaries (the same way our project tools do), then price them as above. We do not keep the file.
Does biodiversity net gain apply?
The check asks one question at a time and stops as soon as your answers decide. It applies these exemptions in this order. Each one is a dated rule we update when gov.uk changes.
| Exemption | Rule | Source |
|---|---|---|
| Householder applications are exempt | Small projects at a home, such as extensions, conservatories and loft conversions (householder applications as defined in the Development Management Procedure Order 2015), do not need biodiversity net gain. | gov.uk |
| Biodiversity gain sites are exempt | Development that creates or enhances habitat solely or mainly to provide off-site gains for other developments does not need biodiversity net gain itself. | gov.uk |
| High speed rail is exempt | Development that is part of, or ancillary to, the high speed railway transport network is exempt. | gov.uk |
| Permission by a development order is exempt | Development granted planning permission by a development order, including permitted development rights, is exempt under the Environment Act 2021. | gov.uk |
| Urgent Crown development is exempt | Urgent Crown development is exempt under the Environment Act 2021. | gov.uk |
| Not yet mandatory for this NSIP | Biodiversity net gain becomes mandatory for nationally significant infrastructure projects whose development consent order application is made on or after 2 November 2026. Earlier applications are not caught, although policy may still expect gains. | gov.uk |
| Applied for before biodiversity net gain began | Planning applications made before 12 February 2024 are exempt from biodiversity net gain. | gov.uk |
| Small development applied for before 2 April 2024 | Small (minor) developments applied for before 2 April 2024 are exempt from biodiversity net gain. | gov.uk |
| Self-build or custom build applied for before 6 August 2026 | The self-build and custom build exemption ended for applications made on or after 6 August 2026. Applications made before then stay exempt (a later variation of an exempt permission is also exempt: check with your planning authority). | gov.uk |
| Temporary development of 5 years or less | From 6 August 2026, development where the whole development is temporary and permission is for 5 years or less is exempt, unless it affects priority habitat on the site. | gov.uk |
| Sites of 0.2 hectares or less | From 6 August 2026, development where the site area within the red line boundary is 0.2 hectares or less is exempt, unless it affects priority habitat on the site. | gov.uk |
| Very small impact on habitat (de minimis) | Development that affects less than 25 square metres (5 m by 5 m) of habitat and less than 5 metres of hedgerow or other linear habitat on the site is exempt, unless it affects priority habitat. You need evidence to show this. | gov.uk |
If no exemption applies, we work out whether the development is minor or major using the planning definition (Development Management Procedure Order 2015, article 2): 10 or more homes, or a site of 0.5 hectares or more when the number of homes is not known; 1,000 square metres or more of new floor space; a site of 1 hectare or more; minerals or waste development. A minor development can use the Small Sites Metric
A simpler version of the statutory biodiversity metric for minor developments (for example up to 9 homes on under 1 hectare) with no priority habitat, protected sites or European protected species. A competent person, not always an ecologist, can complete it. Learn more about Small Sites Metric when there is no priority habitat, only habitats it lists, no statutory protected sites and no European protected species (Small Sites Metric user guide, July 2025). From 6 August 2026, a minor development can go straight to off-site units. The check is not legal advice; your planning authority decides.
What your land could earn
Units come from the statutory metric's own formula for creating a habitat: area × distinctiveness score × condition score × difficulty of creation × the temporal multiplier for the years it takes to reach that condition × strategic significance, minus the units the land has today (area × distinctiveness × condition × strategic significance). Low, middle and high assume the new habitat reaches poor, moderate and good condition, or the nearest the metric allows. Every factor is taken from the official metric workbook (The_Statutory_Metric_Macro_Disabled_1.0.4.xlsx, sheets "G-1 All Habitats", "G-3 Multipliers", "G-4 Temporal multipliers" (Defra/Natural England, OGL)).
Price per unit is, in order: your own figures; asking prices of listings on BNG Online for the same habitat (or broad habitat); prices agreed in at least 3 deals on BNG Online; then published market prices for the habitat (or its broad habitat), as for the cost calculator.
Value is units × price, a one-off amount received as units sell. What you might keep takes away the costs below and our fee of 3% of each sale. It is before tax and does not include other income the land could earn, which you may be able to combine with BNG if the same work is not paid for twice.
| Figure | Starting value | Where it comes from |
|---|---|---|
| Baseline habitat survey | £900 a hectare | Defra, Biodiversity net gain impact assessment (2019): survey cost per hectare. 2019 prices, not inflated. Source (our starting figure, still being reviewed) |
| Creating the habitat and managing it for 30 years | £19,698 a hectare | Defra, Biodiversity net gain impact assessment (2019): net present value of 30 years of creation and maintenance, per hectare. 2019 prices, not inflated. Source (our starting figure, still being reviewed) |
| Ecological baseline report and habitat management and monitoring plan (HMMP) | £6,246 for the site | Huntingdonshire District Council, Habitat Banking Programme report (Bio4All pilot): ecological baselining and HMMP per site. Source (our starting figure, still being reviewed) |
| Monitoring fee to the council for 30 years | £17,588 for the site | Tendring District Council, BNG habitat bank fees 2025/26: monitoring for sites under 20 hectares (years 2, 5, 10, 15, 20, 25 and 30). Councils set their own fees. Source (our starting figure, still being reviewed) |
| Registering the site on the biodiversity gain sites register | £639 for the site | Natural England registration fee (gov.uk, Register a biodiversity gain site). Source |
| Legal agreement (section 106 or conservation covenant) | Not included | We have found no published figure; enter your solicitor's quote. |