Floor-area ratio calculator

How it works

Floor-area ratio divides the counted floor area by the site area, using the same area unit for both. A 7,500 m² floor-area total on a 1,000 m² site gives a ratio of 7.5. A 2,500 m² total on that site gives 2.5. The result has no unit.

Worked example

Equal ratios can describe very different buildings. A compact taller building and a lower, more extensive building may have the same total floor area. FAR alone does not tell you building coverage, height, daylight, setbacks, open-space quality or the number of storeys.

Before using the result

For a statutory calculation, replace the generic floor-area input with the area counted under the local rule. Basements, parking, balconies, plant rooms and exemptions can be treated differently. This arithmetic calculator does not establish a permitted development envelope or approval.

More useful references

Drawing scale converter

Square metres and square feet converter

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