Free calculator
GDV calculator
GDV, gross development value, is what a property will be worth once the work is done. Every refurb, flip and BRRR appraisal hangs off it: get the GDV wrong by 10% and the profit figure underneath it is fiction. This calculator estimates GDV the way a sensible valuer does, from the median of comparable sold prices, with a price-per-sqft cross-check when you know the floor areas.
GDV calculator
If the two figures disagree badly, the comps probably span different property sizes or conditions. Trust the price-per-sqft figure when your floor area is measured, and dig into which comps genuinely match before believing either.
How the calculation works
Enter the sold prices of properties genuinely comparable to yours after refurbishment: same area, same type, similar size, sold recently, in the finished condition you are aiming for. The calculator takes the median, the middle value, rather than the average, because one unusual sale drags an average around but barely moves a median.
If you add floor areas, it also works out each comparable's price per square foot, takes the median of those, and multiplies by your property's own floor area. That second route corrects for size differences between your property and the comps; a 1,400 sqft four-bed and a 950 sqft four-bed are not the same deal even on the same street.
We deliberately do not take the top of the range. A refurbished-finish premium has to be earned by comparables in that condition actually selling for more, and by a refurb budget that gets your property to that standard. Pricing the end value off the best sale on the street is the single most common way appraisals go wrong.
Choosing comparables that count
The output is only as honest as the comps you feed it. Three good rules: stay within about half a mile in a town or city, stay within six to twelve months of today, and match the property type exactly; a mid-terrace is not evidence for an end-terrace with a side plot, let alone a semi.
- Use sold prices from the Land Registry, not asking prices; asking prices are marketing
- Prefer comps in refurbished condition when valuing a post-refurb GDV
- Three comps is a minimum, five or more starts to be reliable
- If the range is wide, believe the median, and ask why the outliers sold where they did
Frequently asked questions
What does GDV mean in property?
Gross development value: the open-market value of a property or scheme once building or refurbishment work is complete. Developers use it to size deals and lenders use it to set loan amounts, typically capping development finance at 60 to 70% of GDV.
How do I calculate GDV on a refurb?
Find recent sold prices for comparable properties in finished condition, take the median, and cross-check against median price per square foot multiplied by your floor area. If the two figures disagree badly, your comps probably span different sizes or conditions.
Why use the median and not the highest comparable?
Because the highest sale usually had something yours does not: a bigger plot, a better spec, a bidding war. The median is what the evidence supports; the top of the range is what you hope for. Lenders and surveyors value on evidence.
Where do I find sold prices and floor areas?
Sold prices are public through the Land Registry and show on the main portals. Floor areas come from floorplans on old listings or from the EPC register, which records total floor area for most UK homes.
Want this run automatically on any Rightmove listing?
PropDetect runs these numbers, and the rest of the deal, on every listing that matches your criteria: refurb costs from the photos, comparable sold valuations, rent, GDV and a strong, solid or avoid verdict across six strategies. You just read the result.
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