NutrientMonkey
Nutrient Neutrality Calculator
Start here. The protected site the scheme drains to and the nutrient it is assessed for — every default below follows from this choice.
The LPA's nutrient-neutrality advice note names it — it is the document that told you an assessment was needed in the first place. Failing that, use our catchment map or ask the case officer.
Be careful near boundaries. Phosphorus-led River Avon runs right alongside nitrogen-led Poole Harbour, and Stodmarsh and The Broads are assessed for both nutrients at once. Picking the neighbour gives you a confident answer for the wrong nutrient.
Share of the discharge: leave it at 100 unless the authority has told you a treatment works sends only part of its effluent into the protected catchment. Credit price: entirely optional, never appears on the report.
For the report header only — none of it changes the budget.
No. Step 2 is the report header and nothing more — you can leave it blank while you work out the figures. It is worth filling in before you export, so the PDF reaches the case officer with the site, applicant, authority and reference already on it.
Water in. What the new dwellings will discharge — from occupancy, water use and the treatment works' permit.
This step produces most of your budget, so it is the one worth slowing down on.
Why the permit boxes start empty. On mains drainage the works' consent sets most of the budget, and NE's standard consent at first occupancy is commonly 27 mg/l. Rather than open on a plausible-looking default and hand you a budget a third too low, the tool waits until it has the real one. Pick your works and the waiting stops.
The land today. Only the land whose use the development changes. Natural England’s own export coefficients fill in by themselves once the site details are set.
Only the land whose use is actually changing — not the whole holding, and not the parts of the red line that stay as they are. Areas are in hectares (1 ha = 10,000 m²), so a single house plot is usually 0.03 to 0.08 ha. Measure them off the site plan; most CAD and GIS packages give a closed polygon's area directly.
Land use type — the closest match to what is on the ground today: cereals, lowland grazing, dairy, woodland, gardens (greenspace). The list is Natural England’s own for this catchment.
The coefficients are Natural England’s, looked up exactly as NE’s calculator does it: by rainfall for urban land; 0.02 kg P and 3 kg N per hectare for greenspace, woodland and shrub; and by operational catchment, farm type, NVZ, rainfall and soil drainage for farmland. Rainfall is already set to the figure NE’s workbook names for this catchment. You only need the soil drainage type (Soilscapes map) — and, for farmland, whether the site is in an NVZ. If you have site-specific evidence for a different coefficient, ✎ lets you type your own; the report marks it as yours.
The same land afterwards. The land cover present on that area once built (e.g. residential urban land, open urban land, greenspace).
This is the same piece of ground as step 4, described again — so the areas here should total the same as the areas there.
The coefficients are Natural England’s, as in step 4: urban land by the rainfall band, greenspace, woodland and shrub at NE’s fixed 0.02 kg P / 3 kg N per hectare, water at nil.
Water out. Nutrient taken back out of the post-development surface-water load by drainage features. Leave at 0 if there are none.
Leave both boxes at zero. That is the conservative answer and nobody will challenge it — it simply means you are claiming no credit for drainage.
Only enter a figure when a drainage engineer has assessed it, using CIRIA C815 (nitrogen) or C808 (phosphorus) removal rates. A claimed removal with no assessment behind it is exactly the kind of thing that comes back from the LPA's ecologist.
The answer. (waste water − current land use + future land use − SuDS) × 1.2 precautionary buffer.
CREDITS NEEDED is the normal outcome for new homes in a sensitive catchment — it is not a failure, it is the number of credits you need to buy. One credit offsets 1 kg of nutrient per year, so the budget in kg/yr is the credit requirement.
Where a works’ permit tightens — usually on 1 April 2030, earlier at a few works with a WINEP upgrade date — you get two budgets. Buying permanent credits only, you need the greater of the two. Or split it: temporary credits for the excess until the upgrade, plus permanent credits for the enduring baseline — often cheaper where a scheme sells temporary credits at all.
The figures are Natural England’s own — the same permits, lookups and arithmetic as NE’s calculator for the catchment — so they reproduce in it exactly. Working on screen is free for as long as you like, and Copy budget summary gives you the figures as plain text for an email. You only pay to export the planning-ready PDF.
Free to use on screen. See an example report
Got your budget? Work out how many credits it buys and what they cost: the nutrient credits calculator → · published scheme prices by catchment and provider
New to nutrient budgets? The explains every box and where each number comes from, and there is a longer step-by-step guide on the website.
Nutrient neutrality means a new residential development will not cause a net increase in nutrient pollution to a protected habitats site. Natural England catchments are assessed for nitrogen, phosphorus, or both — e.g. Poole Harbour and the Solent (incl. Chichester Harbour) are nitrogen; the River Avon (which discharges into Christchurch Harbour) is phosphorus; Stodmarsh, The Broads and the River Itchen are both. Where a catchment requires both nutrients this tool calculates both budgets at once; they remain two independent budgets, each mitigated with its own credits. The nutrient budget is (waste water − current land use + (future land use − SuDS)) × 1.2, where the ×1.2 is Natural England's 20% precautionary buffer. Waste-water load = occupancy × units × water use (l/p/d, incl. NE's +10 l/p/d allowance) × 365.25 × permit (mg/l) × 0.9 ÷ 1,000,000 — Natural England assumes a works discharges at 90% of its permit, and takes the no-permit defaults (27 mg/l N, 8 mg/l P) at face value. Permits come from NE's Stage 1 WwTW lookup for the catchment, with the upgraded figure from each works' WINEP date; for off-mains, NE's default total-nitrogen concentrations are 96.3 mg/l (septic tank) and 72.9 mg/l (package treatment plant), and total-phosphorus 11.6 mg/l and 9.7 mg/l. Land-use export coefficients are NE's own Stage 2 and 3 lookups — by operational catchment, farm type, NVZ, rainfall band and soil drainage — and the loads and budgets are rounded as NE's workbook rounds them, so every figure here reproduces in the official Natural England calculator for the catchment. One credit mitigates 1 kg of the nutrient per year. Where the local planning authority or Natural England require the statutory submission, these figures are entered in the official Natural England calculator; the report lists exactly what to enter. It does not replace ecological, drainage or engineering advice.
A fully-branded, planning-ready PDF: catchment, waste-water load, current & future land use with Natural England’s coefficients, SuDS, the nutrient budget(s) either side of any permit upgrade, the credits required and full methodology notes — plus a page of exactly what to enter in NE’s own calculator to get the same figures. Dual-nutrient catchments include both the nitrogen and phosphorus assessment.
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Secure payment via Stripe · £79 + VAT (20%) = £94.80 total. Included: a planning-ready PDF with a unique Report ID (verifiable at energycount.co.uk/verify), re-download free for 24 hours and free re-export for genuine corrections within 1 hour (up to 5). A VAT invoice is emailed automatically — add your company name and VAT number at checkout. By paying you agree to our Conditions of Sale — the report is supplied immediately, so the 14-day cancellation right is waived on delivery.
You are building one number: the nutrient budget for your scheme, in kilograms per year. If it comes out above zero, that is how much nitrogen or phosphorus you have to offset before the council can grant permission. If it comes out at or below zero, the scheme is already neutral.
There are seven steps on the page, but only three of them really move the answer: the catchment (step 1), the dwellings and water use (step 3), and the land-use change (steps 4 and 5). Everything else is either a header, an option, or worked out for you.
Every box on the page has a small i beside its label. Click it and it tells you what the number is, why it matters, and exactly where to get it. Nothing is hidden behind a login and nothing is charged until you export the PDF.
Natural England's methodology compares the nutrient your development will discharge with the nutrient the land already exports, and adds a precautionary margin:
budget = ( waste water − current land use + future land use − SuDS ) × 1.2
The waste-water term dominates for new housing: occupancy × dwellings × water use (l/p/d, including NE's +10 allowance) × 365.25 × permit × 0.9 ÷ 1,000,000 — Natural England assumes a works discharges at 90% of its permit (27 mg/l N and 8 mg/l P, the no-permit defaults, are taken as they are). The ×1.2 is Natural England's 20% precautionary buffer, and it is not optional. Every figure is rounded the way NE's own workbook rounds it, so your budget reproduces in NE's calculator exactly.
One credit offsets 1 kg of nutrient per year. So the budget in kg/yr is the number of credits you need.
Pick the Natural England catchment the site drains into. This one choice decides whether you are assessed for nitrogen, phosphorus or both, which treatment works appear in step 3, whether a 2030 permit step applies, and what the indicative credit price is.
Where to get it: the LPA's nutrient-neutrality advice note names the catchment, or use our catchment map. Be careful near boundaries — the phosphorus-led River Avon runs right alongside nitrogen-led Poole Harbour, and picking the wrong one gives you a confident answer for the wrong nutrient.
Share of the discharge is 100 for most sites. Only change it where the authority has told you a treatment works sends just part of its effluent into the protected catchment — it can be as low as 0.13% (Canterbury, May Street). Choosing a sub-area, where the catchment has them, fills it in for you.
Credit price is optional and never appears on the report. It exists so you can see what the shortfall will cost. Check the unit: some schemes quote per kg, some per 0.1 kg.
Report header only. None of it changes a single figure. Fill it in before you export so the PDF arrives at the case officer with the site, applicant, authority and reference already on it.
This is where most of the budget comes from, and the step worth slowing down on.
| Box | What to enter | Where it comes from |
|---|---|---|
| Dwellings | Number of new dwellings the application creates | Your drawings. For a replacement dwelling, ask the LPA how they treat the existing load |
| Occupancy | 2.4 people per dwelling unless told otherwise | NE's default. Canterbury accepts 1.6 for flats at Stodmarsh; Cumbria sets its own rates from 1 May 2026 |
| First occupancy | When the first home will be lived in | Your programme. It selects which permit tier applies — before 1 January 2025, up to the works’ upgrade, or after it |
| Water standard | 110 (NE’s default) or 125 l/p/d | Your planning conditions. NE adds +10 l/p/d on top automatically |
| Drainage | Mains, septic tank or package plant | Your drainage strategy |
| Treatment works | Pick it from the list | Your sewerage undertaker confirms which works serves the site |
| Permits | mg TN/l and mg TP/l, at first occupancy and after any upgrade | Filled automatically when you pick the works — otherwise the Stage 1 WwTW tab of NE's own catchment workbook. Not sure which works? Step 7 shows the range across all of them meanwhile |
Why the tool waits for a permit. On mains drainage the works' consent sets most of the budget. NutrientMonkey deliberately opens those boxes empty and refuses to produce a figure until it has a real consent, rather than starting on a plausible-looking default that would quietly make your budget wrong by a third. Pick the works and the waiting stops.
Off mains, Natural England publishes the concentrations for you: 96.3 mg/l TN and 11.6 mg/l TP for a septic tank, 72.9 and 9.7 for a package treatment plant. Pick the "NE default" option and there is nothing to look up. Use "manufacturer value" only if you hold a certificate for a better-performing plant.
These two tables describe the same piece of ground twice: how it is used today, and what will cover it once the scheme is built. Only include land whose use is actually changing — not the whole holding, and not the parts of the red line that stay as they are. The areas in step 5 should total the same as the areas in step 4.
Areas are in hectares (1 ha = 10,000 m²), so a single house plot is usually 0.03 to 0.08 ha. Measure them off the site plan.
The export coefficients are Natural England’s own. They say how much nutrient each land use leaches per hectare per year, and NE sets them by operational catchment, farm type, NVZ status, rainfall band and soil drainage. NutrientMonkey carries NE’s lookups for every catchment and reads them exactly as NE’s calculator does: set the soil drainage type in step 4 (the rainfall is already set to the figure NE’s workbook names), answer the NVZ question if the land is farmed, and every coefficient fills in. Have site-specific evidence for a different figure? ✎ lets you type your own, and the report marks it as yours.
If ponds, wetlands, swales or basins will take nutrient back out of the surface-water load, enter the kg/yr here and the budget drops. If there are none, or the drainage design is not fixed yet, leave it at zero — that is the conservative answer and no ecologist will argue with it. A claimed removal without a drainage assessment behind it is the kind of thing that comes back.
Where to get it: your drainage engineer, using CIRIA C815 (nitrogen) or C808 (phosphorus) removal rates.
Where a works' consent tightens — on 1 April 2030 at most works, on its own WINEP date at a few — you get two budgets, before and after. If you buy permanent credits only, you need the greater of the two. Or you can split it — cheaper temporary credits for the excess until the upgrade, plus permanent credits for the enduring baseline underneath. The tool shows all three figures, and route (b) is often cheaper where a scheme offers temporary credits at all.
Working on screen is free, for as long as you like. Copy budget summary gives you the figures as plain text for an email to your case officer, also free.
The paid export (£79 +VAT) is a planning-ready PDF: catchment, waste-water load, current and future land use with NE’s coefficients, SuDS, the budgets either side of any permit upgrade, the credits required and the full methodology notes — plus a page listing exactly what to type into Natural England’s own calculator and the figure it returns — with a unique report ID your case officer can verify at energycount.co.uk/verify. Dual-nutrient catchments get both assessments in one report. Corrections re-export free for 24 hours.
NutrientMonkey reproduces Natural England's own catchment calculators (the 26 V_03_01 workbooks) across all 27 catchments — NE's permits, NE's land-use lookups and NE's arithmetic, checked against the workbooks themselves — with the working shown line by line so an ecologist can check it. The official Natural England catchment calculator remains the statutory tool, and your figures reproduce in it: the report lists exactly what to enter. It does not replace ecological, drainage or engineering advice.
Stuck on something the tool cannot answer? We are a real consultancy, not just a website — get in touch or call 01202 623236.