Zoning calculator
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.
Lot coverage 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 Assessor figures are often rounded or out of date.
Roofed structures, as your code defines them. Codes differ on garages, porches, and decks.
Driveways, parking, walks, patios. Used for impervious cover only. Codes differ on gravel and pervious paving.
Building coverage
28%
900 sq ft still available under the cap
Impervious cover
40%
Buildings plus paving and other hard surfaces
2,100 ÷ 7,500 sq ft = 28% · (2,100 + 900) ÷ 7,500 sq ft = 40%
Codes measure coverage differently: some exclude eaves, decks, or pervious paving, some set separate limits for accessory buildings, and some let structures sit in part of a setback.
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.
Lot coverage is the share of a lot covered by buildings. Codes set a maximum percentage for each district. Some also cap impervious cover, which adds driveways, parking, and other hard surfaces to the buildings. Divide the covered area by the lot area and multiply by 100 to get the percentage.
How to use the calculator
- Enter the lot area in square feet or acres.
- Enter the combined footprint of the buildings and structures your code counts.
- Enter paving and other hard surfaces if your code limits impervious cover.
- Optionally enter the district's caps to see how much room is left, or how far over the project is.
- Optionally include setbacks to see whether the yards or the coverage cap limit the footprint first. This assumes a rectangular lot with the same setback on every side.
What counts as coverage depends on the code
- Austin regulates two numbers. Building coverage counts buildings and roofed areas and excludes ground-level paving, landscaping, eaves, and balconies. Impervious cover counts any surface that keeps water from soaking in, such as roads, parking, concrete, and buildings.
- New York City counts the part of the lot that, viewed from directly above, is covered by a building.
- Miami counts all buildings, but excludes roof overhangs and other unenclosed cantilevered elements up to seven feet, and structures such as decks, pools, and trellises.
- Detroit counts principal and accessory buildings and structures, as a percentage of total site area. It separately defines impervious surface to include parking, driveways, gravel, and sidewalks.
So the same house can be over the cap in one city and under it in another. Use your code's definitions when you add up the footprint.
Example coverage limits
| City and district | Maximum coverage |
|---|---|
| Austin, SF-3 (family residence) | 40% building coverage, 45% impervious cover |
| Austin, MF-3 (multifamily) | 55% building coverage, 65% impervious cover |
| Austin, GR (community commercial) | 75% building coverage, 90% impervious cover |
| New York City, R6 through R12 | 80% on interior and through lots, 100% on corner lots |
| Miami, T4 / T5 / T6 | 60% / 80% / 80% |
| Detroit, R1 single-family | 35% |
New York City's code includes its own example: on a 20,000 square foot lot split into an interior portion allowed 70 percent coverage and a corner portion allowed 100 percent, the two 10,000 square foot portions can be covered by 7,000 and 10,000 square feet.
Frequently asked questions
What is the difference between lot coverage and impervious cover?
Lot coverage usually counts buildings. Impervious cover counts every hard surface, including driveways and parking. Codes that cap both, like Austin's, set the impervious limit higher.
Does a driveway count toward lot coverage?
Usually not toward building coverage, but it does count toward impervious cover where a code caps it. Check your code's definitions.
Sources
The codes 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.
- City of Austin: Land Development Code Sections 25-1-21 to 25-1-23. Definitions of building coverage, lot area, and impervious cover.
- City of Austin: Land Development Code Section 25-2-492. Building coverage and impervious cover limits by district.
- NYC Department of City Planning: Zoning Resolution Section 12-10. Definition of lot coverage and the worked example.
- NYC Department of City Planning: Zoning Resolution Section 23-362. Lot coverage in R6 through R12 districts.
- City of Miami: Miami 21 Code, Article 1, Section 1.2 and Article 4, Table 2. Definition of lot coverage and limits by Transect Zone.
- City of Detroit: Code Chapter 50, Article XIII and Article XVI. Lot coverage definition, the R1 limit as codified October 9, 2025, and the definition of impervious surface.
Related reading
- 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.
- 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 a Setback in Zoning? Front, Side, and Rear Setbacks Explained
What a zoning setback is, how front, side, and rear setbacks define the buildable area of a lot, how New York City and Texas treat them, and how to find the setbacks for a specific parcel.
- 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.