Marginly
Deal appraisal calculator for UK property developers
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Dave Bateson

Marginly - Deal appraisal calculator for UK property developers

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UK property developers run serious money through precarious spreadsheets. One formula error wipes out your margin. Marginly replaces the spreadsheet. Input your deal and it calculates SDLT at current UK rates, development finance, profit on GDV, and gives you a traffic-light health indicator (Strong / Decent / Tight / High Risk). Compare up to 5 scenarios. Export a branded PDF for investors or lenders. Built for the solo UK developer. No enterprise pricing, no US assumptions.

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Dave Bateson
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Hi Product Hunt! I’m Dave, the solo founder of Marginly. I built this because a developer friend lost money on a deal that looked fine on paper — until a formula error in his spreadsheet said otherwise. It happened mid-project. I’d been watching UK property developers — the small-scale ones, not the big housebuilders — manage serious financial decisions through increasingly complex spreadsheets. There’s no shortage of enterprise tools for institutional developers, and plenty of US-focused real estate software, but almost nothing built for the person doing their first loft conversion or buying their third BTL-to-HMO. Marginly is my attempt at that: SDLT auto-calculated at current rates, real UK build cost benchmarks, development finance modelling that reflects how private finance actually works, and PDF output you’d be happy to show a lender. Would love your feedback — especially from anyone who’s wrestled with a property deal spreadsheet. What am I missing?