How many homes could grey belt deliver?
The government never published an estimate. Independent figures range from 50,000 to 4 million. Here is a transparent model you can adjust, built from the published evidence.
A very wide range.
In February 2025 the House of Lords Built Environment Committee noted that estimates ran "from as low as 50,000 to as high as 4 million" homes, and that the government had not assessed the number. Ministers said they expected the share of Green Belt released to be in "single digits".
Sources: Lords Built Environment Committee (Feb 2025); LandTech (July 2024); LandTech and Stack Data; Inside Housing (Dec 2024).
Adjust the assumptions.
Green Belt area × share that is grey belt × share that comes forward (after constraints, the GB7 tests and plan-making) × net developable area × density. Each starting value is anchored to published evidence.
| Green Belt in England (Mar 2025) | 1,633,220 ha |
| Grey belt | – |
| Coming forward | – |
| Net developable | – |
| Of which affordable (at 50%) | – |
| Share of England's land area built on | – |
Illustrative only, over roughly ten years. The model ignores the separate station route, timing, build-out rates and market absorption.
Low, central, high.
Our three scenarios, compared with the government's target of 1.5 million homes in England in this Parliament.
9% grey belt, 5% comes forward, 30 dph. Close to the "single digits" view and LandTech's narrower 2024 analysis.
15% grey belt, 10% comes forward, 35 dph. Roughly a third of the 1.5 million target, delivered over several years.
20% grey belt (London's figure), 20% comes forward, 40 dph. Would need strong plan-making and many appeals going developers' way.
Why the 2026 changes push estimates up
Removing the footnote 7 exclusion widens what counts as grey belt (Sutton's qualifying parcels doubled from 4 to 8). The station route adds land that need not be grey belt at all. Constraints still apply when schemes are decided, so more land qualifying does not mean proportionately more homes.
Own land in the Green Belt?
Find out whether it could be grey belt, which route to permission might apply, and what the Golden Rules would ask of a scheme.