Calculate maximum buildable floor area from plot area and allowed plot ratio, or check FAR by comparing total floor area to plot area.
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Plot Ratio Formula
Plot ratio, also called floor area ratio or FAR, compares total floor area to the plot area. A higher ratio means more floor area can be built on the same land area.
Maximum buildable floor area
- GFA_max = maximum gross floor area allowed
- A_plot = plot area
- FAR = allowed plot ratio
Use the same area unit for the result as the plot area. If the plot area is in ft², the buildable floor area is in ft². If the plot area is in m², the result is in m².
Check an existing plot ratio
- FAR = plot ratio or floor area ratio
- GFA = total floor area across all counted floors
- A_plot = plot area
The floor area and plot area must use the same unit before dividing. The calculator converts ft² and m² as needed.
Typical Plot Ratio Ranges
Actual limits come from local zoning rules. These ranges are only general reference points.
| Plot ratio | Common density type | Typical building form |
|---|---|---|
| Under 0.75 | Low density | Detached homes, small residential lots |
| 0.75 to 1.49 | Moderate density | Townhouses, small walk-up buildings |
| 1.50 to 2.99 | Mid-rise density | Apartments, mixed-use blocks, 4 to 8 storeys |
| 3.00 to 5.99 | High density | Urban apartment towers, dense mixed-use projects |
| 6.00 and above | Very high density | CBD towers, major transit-oriented sites |
What to Check Before Using the Result
| Item | Why it matters |
|---|---|
| Gross floor area definition | Some rules exclude parking, balconies, plant rooms, or basements. |
| Site coverage | A project can meet FAR but still exceed ground coverage limits. |
| Height limit | The allowed floor area may not fit if the height cap is low. |
| Setbacks and open space | Required yards, buffers, and open areas reduce the usable building envelope. |
| Bonus floor area | Affordable housing, public space, or transit bonuses may change the allowed ratio. |
Plot Ratio Example
If your plot area is 8,000 ft² and the allowed plot ratio is 2.5, the maximum buildable floor area is:
8,000 × 2.5 = 20,000 ft²
That 20,000 ft² is the total counted floor area across all floors, not the footprint of the building. For example, a 5,000 ft² footprint over 4 floors also gives 20,000 ft² of total floor area.
