The underwriting toolbox
From postcode to go/no-go in 3 minutes.
Not 3 hours of Excel.
13 free calculators across the four stages of UK development underwriting. Site assessment, cost, returns, exit. All of them feed into a single Quick Check report you can save and share with a JV partner or bridging lender.
Start here · The Quick Check
Underwrite a postcode in one pass.
Postcode and asking price in. GDV, build cost, SDLT, planning flags, and ROI out. Same answer whether the source is Rightmove, Allsop, SDL, Savills, Barnard Marcus, or an off-market deck. About 30 seconds of typing, about 3 minutes of reading the report.
Quick Check report
SW9 2A
0.18 acres · consent for 4 units
GDV
£1.42m
Gross margin
21.8%
ROI
19.4%
Build cost £812k · SDLT £19,250 · 5-year hold, sale exit
The underwriting flow
Four stages. Eleven calculators. One report.
Open any calculator on its own, or run Quick Check above and let it pull from the same engines in one pass.
Site assessment
Is the site viable before you book the viewing.
Area Check
Postcode in. Transport, classification, and flood exposure out. The constraints that kill schemes before they reach planning.
Open the calculatorRisk score
72
/ 100 · SW9
Site Feasibility
Constraints, nearby planning history, refusal patterns, and a planning risk grade for the postcode. The planning read before you commit.
Open the calculatorRisk grade
B
score 74 / 100
Planning Check
Article 4 directions, CIL schedule, PDR status. Live from planning.data.gov.uk, not last year's PDF.
Open the calculatorPlanning flags
0 / 4
Article 4 · Conservation · PDR · CIL
Comparables
Land Registry sold prices on the same street, refined for property type, sqft, and condition. The GDV your lender will accept.
Open the calculatorGDV
£612k
3 comps · SW2 · 2024
Cost
What it actually costs to build, before the QS quote.
Build Cost Estimator
28 trades, three quality tiers, regional multiplier baked in. RICS-benchmarked. Run it for free on the deal you haven't won yet.
Open the calculatorBuild cost
£812k
1,800 sqft · London · mid spec
Stamp Duty (SDLT)
Run an SDLT against your asking price. Individual, first-time buyer, company SPV, second home. The 3% surcharge is in the maths, not a footnote.
Open the calculatorSDLT
£19,250
£495k · company SPV
EPC Impact
Model the band shift before you spend on the retrofit. How a D to B move changes valuation, lender appetite, and rentability.
Open the calculatorValue uplift
+£42k
D → B · 1,800 sqft
Lease Extension
Premium estimate with marriage value and the 80-year cliff warning. Know what you're buying before the auction hammer drops.
Open the calculatorPremium
£28,400
78 yr · £450k flat
Returns
Does the scheme pay back. ROI, yield, cash left in.
BRRR
Buy, refurb, refinance, rent. One cycle modelled in full. The number you actually care about: cash left in after refinance.
Open the calculatorCash left in
£12,800
£260k · 12 mo cycle
Rental Yield
Gross and net yield with voids, management, and mortgage subtracted. The yield the lender models, not the brochure number.
Open the calculatorNet yield
5.8%
after voids + mgmt
Exit
Flip, hold, or convert. Pick the exit before you commit.
Flip
Buy, refurb, sell. SDLT, bridging, fees, and CGT modelled in. The number you keep, after every line of cost.
Open the calculatorNet profit
£78,400
9 mo · 22% margin
Commercial to Residential
Class MA or full planning conversion. Regional build costs and a planning-risk premium against the as-built GDV.
Open the calculatorROI
24.6%
Class MA · 4 units
One report, not eleven tabs
The calculators all feed into Quick Check.
Run them on their own when you only need one number. Run them together when you're deciding whether to book the viewing, send the offer, or walk. The output is the same report you forward to your JV partner.
Quick Check report
One page · one verdict · one link to share
Build-cost guide
28 trades. 11 UK regions. The number before you call the QS.
We’ll send the regional UK build-cost PDF, RICS-benchmarked, segmented by region. One click to unsubscribe.
Free Build Cost Guide
28 trades · RICS-benchmarked · segmented by region
No spam. Unsubscribe anytime.
Honest bit
What the calculators won’t do
They won’t replace a QS on the deal you actually pursue, they won’t draft your JV waterfall, and they won’t tell you whether the vendor is bluffing. What they will do is screen ten deals in the time it used to take to model one, so the QS fee and the legal time get spent on the deal that’s worth them.
Looking for area data? Browse UK postcode districts.