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Floor Area Ratio Calculator

Determine the various area indices for your new home using the floor area ratio calculator.

Clear
Floor area ratio0.66,000 ÷ 10,000 sq ft
As a percentage60%
Gross floor area6,000 sq ft
Lot area10,000 sq ft0.2296 acres
Floor area permitted8,000 sq ftFAR 0.8 × 10,000 sq ft
Resultwithin the limit2,000 sq ft still available
FAR used75% of the allowance
Lot coverage25%footprint as a share of the lot — a separate limit from FAR
Storeys implied2.4gross floor area ÷ footprint
Open space7,500 sq ft75% of the lot

The formula

FAR = gross floor area ÷ lot area

Bulk, not shape

Floor area ratio limits how much floor you may build relative to the land, and it says nothing about how you arrange it. An FAR of 1.0 on a 10,000 square foot lot permits a single storey covering the whole plot, two storeys over half of it, or ten storeys on a tenth — all the same FAR.

That is why FAR almost never appears alone. Height limits, setbacks and lot coverage do the work of controlling the shape, while FAR controls the total quantity.

What counts as gross floor area varies by jurisdiction. Basements, parking, mechanical space and balconies are sometimes excluded and sometimes not, and the definition matters more than the arithmetic — check the local code.