Estimate your
building lot coverage.
Enter your lot area and building footprint changes to compare existing and proposed building-coverage percentages. This calculator does not determine your zoning allowance.
Educational estimates only. Check local classification and source measurements before using results for a permit.
Lot Coverage Calculator
Replace the sample inputs with your own measurements. Calculations update as you type; nothing is transmitted or stored.
Enter your areas
Use square feet. Zero means none. Negative values aren’t accepted.
YOUR ESTIMATED COVERAGE
Enter valid figures to see an estimate.
Request a Site Plan Quote ↗Not a certified calculation or determination of regulatory compliance.
Understand the percentage.
For a fictional 10,000 sq ft lot with 2,200 sq ft of existing building footprint and 350 sq ft added, the estimate becomes 25.5%.
Proposed counted area = existing counted area + proposed additions – existing counted area removed.
Estimated coverage (%) = proposed counted area ÷ lot area × 100.
What counts as a building or impervious surface is determined by the relevant local ordinance, not this page. Do not assume this percentage establishes permit eligibility.
Check the result before relying on it.
Confirm lot area
Use an appropriate survey or documented parcel area, then check whether local calculation adjustments apply.
Identify counted buildings
Measure existing and proposed roofed or enclosed areas according to the local definition.
Compare the result
Review the estimated percentage against the verified ordinance and submitter’s guidance.
What the result means.
These estimates are useful for planning and discussion with your permitting authority, not a substitute for a project-specific professional review.
Does this calculator determine whether a project is permitted?
No. It calculates a simple ratio. Zoning, stormwater, setbacks, overlays and the governing local definitions must be reviewed separately.
Does a deck count toward building coverage?
That depends on the applicable local ordinance and whether the structure is covered or otherwise included in the local building-coverage definition.
Should I use survey lot area?
Reliable property documentation is preferable. A screenshot or rough GIS estimate is not automatically a certified property area.
Need a site plan for your real property?
Send the address, property information and proposed improvements. We can discuss the drawings and coverage schedules appropriate to your project.