How this calculator works
FAR divides total counted floor area across all storeys by lot area. Unit mode builds that total from carpet area, wall area and common floor area, with common space allocated equally to identical units. Loading factor is defined here as allocated gross area divided by carpet area minus one. Open space ratio is open lot area divided by counted floor area. Local definitions can exclude some spaces, so use consistently counted inputs.
Formula
FAR = counted floor area / lot area; total floor = units x (carpet + walls) + common area; allocated gross per unit = total floor / units; OSR = open space / total floor.
Worked example
A building with 2000 m2 of counted floor on a 1000 m2 lot has FAR 2.0. If open space is 300 m2, the open-space-to-floor ratio is 0.15.
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Frequently asked questions
Is FAR the building footprint coverage?
No. FAR adds counted floor space on every storey. Footprint coverage describes ground occupied by the building.
Are common areas always counted?
Local zoning rules decide what counts. This form includes the common area you enter and does not interpret a zoning bylaw.
Can I find the floor area allowed by a target?
Yes. Multiply the permitted FAR by the lot area using total-floor mode. Other limits such as height and setbacks still apply.