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Guide

How to calculate buildable square footage and max FAR in NYC

The single most important number in any NYC feasibility study is the maximum buildable floor area. Here’s how it’s actually calculated — the formula, the traps that reduce it, and the bonuses that raise it.

The FAR formula

Floor Area Ratio (FAR) is the ratio of a building’s total zoning floor area to the area of its lot. The base formula is simple:

Maximum floor area = lot area (SF) × FAR. A 5,000 SF lot in a district with a residential FAR of 3.0 has a base maximum of 15,000 zoning square feet. Each use — residential, commercial, community facility — can have a different FAR, and the controlling one depends on what you intend to build.

Why the FAR number is usually too high

The FAR math gives a ceiling, but three things routinely stop you from reaching it. Height limits and setbacks cap how much you can stack. Sky-exposure planes and required yards and courts carve volume out of the buildable envelope. And lot coverage limits restrict how much of the lot each floor can occupy.

On many NYC lots — especially narrow, shallow, or irregular ones — the real buildable area is meaningfully below the raw FAR figure. Any credible calculation has to fit the floor area into a physical envelope, not just multiply two numbers.

  • Height and setback rules limit vertical stacking.
  • Sky-exposure planes and yards remove buildable volume.
  • Lot coverage caps per-floor footprint.
  • Zoning floor area excludes certain mechanical, cellar, and other deductions.

What raises the number

Several programs let you exceed the base FAR. Inclusionary housing and other affordability bonuses, City of Yes provisions, community-facility floor area, and transferable development rights (air rights) purchased from an adjacent lot or landmark can all increase the buildable area — if the lot qualifies.

  • Inclusionary housing / MIH bonuses.
  • City of Yes for Housing Opportunity provisions.
  • Community-facility floor area, where permitted.
  • Transferable development rights (air rights) via merger or adjacent donor lots.

Getting the real number

The honest buildable square footage is the lower of what FAR permits and what the physical envelope can contain, adjusted for any bonuses and air rights the lot qualifies for. Envelope computes all of this from the NYC Zoning Resolution automatically — enter an address and get the max FAR, the buildable square footage after the envelope check, every qualifying bonus, and a 3D massing that proves the number is real. Reports start at $149 with no subscription.

Frequently asked

How do you calculate maximum FAR for a NYC property?

Multiply the lot area by the district’s FAR for your intended use. That gives the base maximum zoning floor area. Then add any bonuses or air rights the lot qualifies for, and confirm the physical envelope (height, setbacks, yards) can hold that floor area.

Why is my buildable square footage less than lot area × FAR?

Because height limits, setbacks, sky-exposure planes, required yards and courts, and lot-coverage caps can prevent you from stacking the full permitted floor area. The buildable envelope, not the FAR math, is often the binding constraint.

What is zoning floor area vs. gross floor area?

Zoning floor area is the measure FAR applies to, and it excludes certain spaces (mechanical areas, cellars, and other deductions) that gross floor area includes. Feasibility uses zoning floor area to check FAR compliance.

Can I increase buildable square footage on a NYC lot?

Sometimes — through inclusionary housing or other bonuses, City of Yes provisions, community-facility floor area, or by acquiring transferable air rights from an adjacent lot. Eligibility depends on the district and the specific lot.

Get the real buildable number for your lot

Envelope computes max FAR, buildable square footage, bonuses, and air rights — and proves it with a 3D massing. From $149, no subscription required.

Run a report — $149 How zoning reports work