# What is building density?
**Building density (also called site coverage or plot ratio) is the ratio of the built-up ground area to the total area of a building plot or plan area.** It is expressed as a percentage or a number between 0 and 1. A building density of 0.4 (or 40%) means that 40% of the site may be covered by buildings.
## Calculation
**Building density = built-up area ÷ total site area**
Only the ground-floor footprint of buildings counts — not the total floor area across multiple storeys.
## Application
Building density is specified in local planning documents (zoning plans) and determines:
– **How much you can build** — the maximum footprint of buildings on your plot
– **Space for green** — the ratio of built to unbuilt land
– **Neighbourhood character** — low density gives a green, open character; high density creates an urban character
### Example
On a plot of 500 m² with a building density of 0.5, the maximum building footprint is 250 m².
## Difference from Floor Area Ratio (FAR)
The Floor Area Ratio (or Floor Space Index) counts all storeys. Building density only concerns the footprint at ground level.
## Related terms
– Zoning plan
– Building permit
– Building line
– Building plot
– Urban design
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