Development finance calculator
This development finance calculator will estimate a scheme's loan to cost, loan to GDV, finance cost and profit from your own figures. The calculator is coming soon; the guide below explains each input.
Reviewed by David Sampson, Founder & Director · Created 19 October 2026 · Last reviewed 19 October 2026
What will the development finance calculator show?
A development finance calculator estimates how a project's costs, loan and profit fit together. Enter the site cost, build costs, fees and contingency, the gross development value and your own finance terms. It will show the loan to cost, the loan to gross development value, the interest on staged drawdowns, the total finance cost and the profit margin.
Every figure will be an input, so the result reflects the numbers entered rather than market data. It is a planning estimate, not a quote or a lending decision. How development finance works is explained in the development finance section.
Inputs that drive a development appraisal
The main inputs are the site cost, the build costs, professional fees, a contingency for overruns, the gross development value of the finished units, and the finance terms: the monthly rate, arrangement and exit fees and the term. Small changes to the build costs or the gross development value can change the margin a lot, so testing several scenarios helps.
Interest on development finance is usually charged only on money drawn, so a realistic drawdown programme gives a more accurate finance cost than assuming the full loan is drawn on day one.
Worked example: profit on GDV
For example, take total costs of £900,000, a gross development value of £1,300,000 and a total finance cost of £90,000 (example figures, not market data). The profit is £1,300,000 minus £900,000 minus £90,000, which is £310,000. As a share of the gross development value, that is a margin of about 23.8%.
Lenders look at the margin because it shows how much the scheme can absorb if costs rise or values fall. The worked example ignores sales costs and tax, which reduce the profit in practice. The guide what is development finance explains loan to cost and loan to gross development value.
Using the result
The result helps test whether a scheme works before paying for full appraisals. If the margin is thin, the developer might renegotiate the site price, change the scheme or bring in more equity. Running the figures with higher build costs and a longer term shows how sensitive the profit is to delays and overruns, which are common in development.
Development finance rates and fees vary by lender and scheme, and specialist brokers can obtain real terms for a specific scheme.
Frequently asked questions
How do you calculate development finance?
Lenders work out the total costs and the gross development value, then lend up to a share of each. The lower result sets the facility. Interest is calculated on the money drawn, usually rolled up to the end.
What is loan to cost?
Loan to cost compares the loan with the total project costs, including the site, build, fees and contingency.
What is loan to GDV?
Loan to gross development value compares the loan with the expected value of the finished scheme once it is complete.
What profit margin do development lenders look for?
Lenders set their own requirements, and they vary with the scheme and the lender. A higher margin gives more room to absorb overruns and falling values.
Is the calculator result a quote?
No. It is an estimate based on the figures entered. A lender's offer depends on the scheme, the developer and the valuation.
When will the calculator be available?
The calculator is being built. The guidance on this page explains the inputs and how development finance is sized in the meantime.
Important: Your home may be repossessed if you do not keep up repayments on your mortgage. Information on this page is for general guidance only and does not constitute financial advice.Always verify details directly and seek independent advice before making financial decisions.