Calculate floor area ratio (FAR), also called FSR or plot ratio, from total floor area and lot area, or find the floor area or lot size a FAR allows.

Optional settings
Blank =0. Exclude only area allowed by the applicable rules.

Blank omits capacity comparison.

Blank uses the equal-floor plate when supplied; otherwise footprint outputs are omitted.

Blank omits coverage comparison.

Blank omits value. An arithmetic scenario, not an appraisal or transferable-rights valuation.

Calculator Operations Required Inputs
Calculate Floor Area Ratio Counted Floor Area (gross minus verified exclusions), Lot Area
Solve Counted Floor Area Floor to Area Ratio, Lot Area
Solve Lot Area Counted Floor Area (gross minus verified exclusions), Floor to Area Ratio

Floor to Area Ratio Formula

The following formula is used to calculate the floor-to-area ratio.

FAR = (G - E) / L
  • Where FAR is the floor to area ratio
  • G is gross floor area (all floors); E is the portion verified as excluded under the applicable rules
  • L is the lot area measured under the applicable rules. Width × depth applies only to a rectangular parcel, not an irregular lot or the remaining footprint after setbacks.

Divide counted floor area (gross area minus verified exclusions) by lot area, using matching units. Lot area and buildable footprint are different quantities.

Floor to Area Ratio Definition

A floor area ratio compares counted floor area with lot area; it does not directly determine building height or permitted stories. Ratio/coverage comparisons require the applicable local definitions and caps. Other controls can prevent the arithmetic ceiling from being achieved.

Floor to Area Ratio Example

How to calculate a floor to area ratio?

  1. First, determine the gross floor area.

    Sum floor areas for the gross area, then subtract only exclusions verified under the applicable local rules.

  2. Next, determine the lot area.

    Use the lot area counted by the applicable rules. Width × depth works only for a rectangular parcel; do not substitute the remaining buildable footprint.

  3. Finally, calculate the floor to area ratio.

    Calculate the floor to area ratio using the equation above.

FAQ

What is a floor to area ratio?

A floor to area ratio is a measure of the ratio of a building floor area to the size of the lot of the property.

Floor to Area Ratio Calculator screenshot