Calculate your project cost

Enter project details to calculate fully-loaded costs normalised to a 30-year timeframe.

Part 1 — Describe your project
1. Project details
280 characters remaining
30 years
2. Primary outcome
3. Co-benefits (optional)
4. Delivery
5. Direct costs
15 years
6. Opportunity costs
7. Financing
15 years

Annualised cost of capital

Public Grant 0% ℹNo financing cost is applied to public grants. The 3.5% HM Treasury Green Book discount rate is used to compute the NPV of the project, not as a cost of capital.
Private Investment — ℹUK gilt yield curve + private investment premiumPrivate investment rates apply a 4% premium on top of the gilt yield. This reflects typical equity risk premia for long-duration, illiquid nature-based investments.

TenorGiltPrivate1yr−0.6%3.4%2yr−0.3%3.7%3yr0.1%4.1%5yr0.7%4.7%10yr1.4%5.4%15yr1.7%5.7%20yr2.0%6.0%25yr2.1%6.1%30yr2.2%6.2%40yr1.9%5.9%50yr1.8%5.8%60yr1.8%5.8%
Gilt yields: UK Debt Management Office and Bank of England published yield curves, via giltsyield.com/bond/inflation
Green Book STPR (3.5% real): HM Treasury, The Green Book (2022)
Correct as of April 2026.
Cashflow 0% ℹNo financing cost is applied. Projects funded directly out of operating cashflow carry a 0% rate.
Donation 0% ℹNo financing cost is applied. Projects funded by donations or philanthropic capital carry a 0% rate.
8. Sources
Part 2 — Comparing projects on equal terms
Projects have different natural lifespans. To compare cost-effectiveness across projects on equal terms, all figures are rescaled to a standard 30-year window. Toggle any cost category to see how sensitive the comparison is to these assumptions. ℹYour project lifespan is 30 years. 30 years is the statutory minimum for a Biodiversity Net Gain project under the Environment Act 2021.
9. Cost scaling

Toggle which cost components should scale with the timeframe change. One-off costs (development, capital) typically should not. Ongoing costs (maintenance, opportunity) typically should.

10. Outcome scaling ℹNature outcomes do not accrue in a straight line — a woodland takes decades to mature while a flood barrier delivers most of its benefit immediately. The delivery curve describes how your outcome builds up year by year, and affects how cost-per-outcome is calculated in the Normalised view for projects longer than 30 years.

Shape assignments are derived from field evidence (RSPB, Natural England, Forestry Commission, Environment Agency and others). The justification for your outcome's default shape is shown in the ℹ next to the shape pills.

A default delivery shape is set for your primary outcome. You can change it using the pills — pick whichever shape best reflects how the outcome accrues for your project. Adjust the timing within the evidence-based range using the slider.

Select a primary outcome in section 2 to see its delivery curve.