Formula and input notes
Floor area ratio = counted building floor area ÷ counted lot area
| Input | Practical note |
|---|---|
| Lot area | Use the site area recognized by the applicable zoning definition; public right-of-way, easements, or excluded land may be treated differently by jurisdiction. |
| Total building floor area | Use the gross floor area definition required by the applicable zoning rule; exemptions and measurement boundaries are not inferred here. |
Worked floor area ratio example
Floor Area Ratio Calculator example: 3,725 ft² of counted floor area ÷ 6,000 ft² of lot area = 0.621 FAR. This arithmetic does not decide which areas the jurisdiction counts.
What the converted result represents
Use the ratio to screen a concept, then reconcile every included and excluded area with the controlling zoning definition.
Limits of the geometric model
Jurisdictions differ on basements, parking, mezzanines, balconies, mechanical space, gross versus net lot area, and rounding.
Questions specific to this calculation
Which floor and lot areas belong in FAR?
Enter total floor area counted under the applicable planning definition and the corresponding lot area; both must use the same area unit.