Getting Started

Welcome to Marginly

Marginly is a property development operating system for small UK developers. At its core is a powerful deal appraisal calculator — but it also includes project timeline management, budget and spend tracking, document storage, and team collaboration tools.

The free version of Marginly requires no account. You can start entering deal numbers immediately and get instant results. Sign up for a paid plan to save your deals, compare scenarios, and access the project management tools.

Creating your first deal appraisal

To create your first deal appraisal:

1. Open the app at marginly.co.uk/app. You'll see a blank deal scenario pre-populated with typical default values.
2. Enter the purchase price in the Purchase section. The SDLT will calculate automatically based on the current 2025/26 rates.
3. Tick "Additional dwelling" if this is not your only property (i.e., you already own a home). This adds the 5% SDLT surcharge, which applies to the vast majority of development purchases.
4. Move to the Build section and select your project type. This sets a typical cost-per-m² range. Enter your build area and adjust the cost per m² to match your contractor quotes.
5. In Finance, enter your expected LTV, monthly interest rate, and loan term. If you're using development finance, typical values are 70% LTV, 0.85% per month, 12 months.
6. In Exit, enter your expected GDV (Gross Development Value — the total expected sale proceeds) and selling costs (estate agent + legal + marketing, typically 2–3%).

The profit summary at the top of the screen updates in real time as you type. You'll see gross profit, margin on GDV, ROI, and a health indicator colour-coded as Strong (green), Decent (amber), Tight (orange), or High Risk (red).

Understanding the results

Gross Profit: GDV minus all costs (acquisition, build, finance, selling).

Margin on GDV: Gross profit as a percentage of GDV. This is the standard UK development metric. Target 20%+ for a viable deal.

ROI: Gross profit divided by total costs.

Cash Required: The amount you need to put in from your own funds (total project cost minus the finance facility).

Saving your deal

On the free plan, your deal is not saved — it exists in browser memory only. To save deals persistently, create an account (free) and upgrade to a paid plan. On Starter and above, your deals are saved automatically every time you make a change.

Renaming your deal

Click on the deal name at the top of the screen to rename it. Names like "4 Birch Lane" or "Birmingham flat conversion" are more useful than the default "My Deal" when you have multiple scenarios.