03 / EARLY PLANNING
Floor-area ratio
Explore the arithmetic relationship between floor area and site area.
GAD / FREE CALCULATOR
Floor-area ratio calculator
A working calculator, a clear formula and examples you can check.
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
Calculation stays in this browser. Inputs are not uploaded.
Questions to take into the work
How is floor-area ratio calculated?
Divide the counted floor area by the site area using the same area units. A 7,500 m² floor-area total on a 1,000 m² site gives 7.5; 2,500 m² gives 2.5. The arithmetic also supports floor-space-index or plot-ratio calculations when the applicable definitions match.
Why is FAR different from building coverage or height?
FAR compares floor area with site area; coverage compares the building footprint with the site. Different building heights and footprints can produce the same FAR. For statutory use, verify local rules for counted floor area and exemptions, including any treatment of basements, parking or balconies.
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GAD Editorial · Answers reviewed 2026-10-18