Area Calculator › Floor Area Ratio

Floor Area Ratio Calculator

Work out the floor area ratio (FAR) from a building's floor area and its lot area, the figure zoning rules use to cap density.

Floor area ratio
sq ft
÷
sq ft
FAR0.5
Quick answer
Floor area ratio is the total building floor area divided by the lot area. A 4,000 sq ft building on an 8,000 sq ft lot has a FAR of 0.5. Zoning codes set a maximum FAR to control how much can be built on a site; a FAR of 2.0 means you may build twice the lot area in floor space.

How it works

FAR = building floor area ÷ lot areaboth areas in the same unit
building floor area
total floor space, all storeys added
lot area
the size of the site
FAR
the ratio, often capped by zoning

FAR counts all floors, so a two-storey building covers less ground for the same FAR. Check your local code for what counts as floor area, since basements and garages are sometimes excluded.

Frequently asked questions

What is floor area ratio?

The building's total floor area divided by the lot area, used in zoning.

What is a FAR of 0.5?

The floor area is half the lot area, for example a 4,000 sq ft building on an 8,000 sq ft lot.

Does FAR count every floor?

Yes, all storeys are added together, though some codes exclude basements or parking.

Why does FAR matter?

It caps how much building a lot can hold, shaping density.