Gross Development Value Calculator

Gross Development Value (GDV) calculator: total value of completed development at sale. GDV = number of units × average sale price. 350k average × 12 units = 4.2M GDV. Net realisation = GDV - selling costs (5% typical) = 3.99M. Foundation metric for development feasibility - all financial decisions cascade from GDV.

Example: 12-unit residential development, 350k average per unit. GDV = 4.2M. Sales costs 5% (210k agent fees + legal + transaction costs). Net realisation = 3.99M. Compare to total development cost (land + build + finance + fees). If margin too thin: don't proceed.

GDV estimation methods: (1) Comparable sales (recent similar properties in area). (2) Per-square-foot rates (500/sqft for new build × 1,000 sqft units). (3) Yield-based (if BTL: rent × 20-25 multiple). Always verify with multiple sources - over-optimistic GDV is the most common development failure cause. Reduce headline comp prices 5-10% for conservative case. Better to underwrite conservative GDV and exceed than vice versa.

Quick example

With number of units of 12 and average unit sale value of 350,000 (plus sales costs of 5%), the result is 4,200,000.00. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.

Which inputs matter most

You enter Number of Units, Average Unit Sale Value, and Sales Costs %. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.

What's happening under the hood

GDV = units × average value. Net realisation = GDV - sales costs. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.

Where this fits in planning

This is a "what-if" tool, not a forecast. Use it to test ideas before committing: what happens if the rate is 2% lower than hoped, what happens if you add five more years. The value is in the scenarios you run, not the single answer you get from the defaults.

What this doesn't capture

Steady-rate math ignores real-world volatility. Actual returns are lumpy; sequence-of-returns risk matters most in drawdown; fees and taxes drag on compound growth; and behaviour changes in drawdowns can reduce outcomes below the projection. The number represents one scenario rather than a forecast.