Zoning calculator
Floor Area Ratio (FAR) Calculator for US Zoning
Work out how much floor area a lot's FAR limit allows, how many stories that takes at a given footprint or inside setbacks, or the FAR of an existing or planned building.
Floor area ratio calculator
Example figures are filled in. Replace them with your own.
Best from a survey or recorded plat. Assessor figures are often rounded or out of date.
From the district's development standards. Many districts set no FAR.
Add this to see how many stories the floor area needs.
Floor area the FAR allows
40,000 sq ft
On a 20,000 sq ft lot at FAR 2, before any bonus
20,000 sq ft lot × 2 FAR = 40,000 sq ft
This is a ceiling. Height limits, setbacks, lot coverage, parking, and the code's definition of floor area often allow less, and bonus programs can allow more.
Arithmetic only, on the numbers you enter. Zoning rules and definitions differ by municipality, so confirm them in the local code or with the planning department before relying on a result.
Floor area ratio (FAR) is the total floor area of the buildings on a lot divided by the lot area. Multiply the lot area by the district's maximum FAR to get the most floor area the FAR allows. New York City's zoning code gives the textbook example: a 10,000 square foot lot with a 20,000 square foot building has a FAR of 2.0. For the concept in more depth, see what is floor area ratio.
How to use the calculator
- Enter the lot area in square feet or acres.
- Choose whether you want the floor area a FAR limit allows, or the FAR of a building.
- Enter the district's maximum FAR, or the building's total floor area.
- Optionally enter a building footprint to see how many stories the floor area needs.
- Optionally include setbacks to see the area left inside the yards and the fewest stories needed to use the full FAR. This assumes a rectangular lot with the same setback on every side.
The result is a ceiling, not a design. Height limits, setbacks, lot coverage, and parking often stop a project before it reaches the full FAR.
What changes the answer in real codes
The arithmetic is the same everywhere. The inputs are not, and three definitions move the result:
- Which land area counts. Austin measures FAR against gross site area. Detroit leaves public rights-of-way and street easements out of lot area.
- Which floor area counts. New York City excludes cellars, mechanical space, and some parking. Austin's gross floor area excludes parking facilities and driveways but includes loading docks. Detroit excludes parking inside a principal building and mechanical floor area. Miami works the other way: its Floor Lot Ratio counts floor area above grade, and its definition of floor area includes parking and loading areas.
- Bonuses. Many codes allow more floor area in exchange for affordable housing or other public benefits, so the base FAR is not always the real limit.
Example FAR limits
These show how widely limits range. Codes are amended often, so check the current table for your district.
| City and district | Maximum FAR |
|---|---|
| New York City, R6 | 2.20 base; 3.00 within 100 feet of a wide street; 3.90 with qualifying affordable or senior housing |
| New York City, R10 | 10.00; 12.00 with qualifying affordable or senior housing |
| Austin, CS (general commercial services) | 2:1 |
| Austin, DMU (downtown mixed use) | 5:1 |
| Austin, CBD (central business district) | 8:1, with a downtown bonus program |
| Miami, T6-8 | Floor Lot Ratio 5, plus 25 percent through the public benefits program |
| Miami, T6-12 | Floor Lot Ratio 8, plus 30 percent through the public benefits program |
Frequently asked questions
How do I calculate the maximum floor area for my lot?
Multiply the lot area by the district's maximum FAR. A 20,000 square foot lot at FAR 2.0 allows 40,000 square feet. Then check the code's definitions of lot area and floor area, any bonus program, and the height, setback, and parking rules.
Do setbacks reduce the FAR allowance?
Not usually. FAR is measured on the whole lot. Setbacks limit how much of that floor area fits on each story, so they can push a building taller or stop it short of the full FAR.
Sources
The codes and documents cited on this page were checked on October 20, 2026. Codes are amended often, so confirm the current text before relying on any figure. This page is general information, not legal or design advice.
- NYC Department of City Planning: Zoning Resolution Section 12-10. Definitions of floor area ratio and floor area, the worked example, and the exclusions.
- NYC Department of City Planning: Zoning Resolution Section 23-22. Maximum residential FAR for R6 through R10 districts.
- City of Austin: Land Development Code Section 25-1-21. Definitions of floor area ratio, gross site area, and gross floor area.
- City of Austin: Land Development Code Section 25-2-492. Maximum FAR by district.
- City of Detroit: Code Chapter 50, Article XIII. Sections 50-13-222 (lot area) and 50-13-237 (maximum floor area and exclusions).
- City of Miami: Miami 21 Code, Article 1, Section 1.2. Definitions of Floor Lot Ratio and Floor Area.
- City of Miami: Miami 21 Code, Article 4, Table 2. Floor Lot Ratio and bonuses by Transect Zone.
Related reading
- What Is Floor Area Ratio (FAR)? How to Calculate It and What It Limits
What floor area ratio means in zoning, how to calculate FAR, what counts as floor area, how New York City and Austin apply it, and what it tells a developer about how much a site can hold.
- Lot Coverage Calculator for US Zoning
Work out building coverage and impervious cover as a share of a lot, how much more footprint or paving a zoning cap allows, and whether setbacks or the cap limit the footprint first.
- Units Per Acre Calculator (Residential Density)
Work out how many dwelling units a site allows under a units-per-acre cap or a minimum lot area per unit, or the density of a planned project, using gross or net acreage.
- What Is Mixed-Use (MU) Zoning? Mixed-Use Districts and Properties Explained
What mixed-use zoning allows, how vertical and horizontal mixed-use differ, how Austin, Detroit, Miami, Phoenix, and Denver define their mixed-use districts, and what developers and investors can do with MU-zoned property.
- Multifamily Site Selection: Finding Land Zoned for Apartments by Right
Which districts allow multifamily by right, how density, height, and parking standards set your unit count, what recent state laws changed, and a parcel search recipe for apartment sites.