Lot Size Calculator

Calculate lot area in square feet and acres with buildable area after setbacks.
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Total Area

9,600 sqft

Acres

0.220

Buildable Area

4,500 sqft

Lot Details

Total Lot9,600 sqft
Buildable Area4,500 sqft
% Usable46.9%

Use the Lot Size Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Our Lot Size Calculator precisely determines your property's total area in square feet and acres, then calculates the critical 'buildable area' remaining after accounting for setbacks. This is crucial for maximizing development potential; for instance, a 2026 residential development in a high-demand urban core might see a 15% increase in property value for every additional 100 sq ft of buildable space.

The calculator first determines total area (Length x Width). Subsequently, it subtracts the perimeter setback area (2 * (Front Setback + Rear Setback) * Lot Width + 2 * (Side Setback + Side Setback) * Lot Length, adjusted for corner lots) from the total area to yield the buildable area. This methodology assumes standard rectangular lots for initial calculation.

Always verify local zoning ordinances, as setback requirements can vary significantly by jurisdiction and property type. A common mistake is assuming uniform setbacks across all property lines; corner lots, for example, often have two 'front' setbacks. Also, consider easements, which can further reduce buildable area beyond standard setbacks.

Example: Calculating Buildable Area for a Residential Lot in Austin, TX (2026)

  1. 1 Input: A lot in Austin, TX, with a length of 120 feet and a width of 80 feet. Zoning requires a 25-foot front setback, a 10-foot rear setback, and 7-foot side setbacks. Let's assume a 2026 property value of $750,000 for the raw land.
  2. 2 Calculation: Total Area = 120 ft * 80 ft = 9,600 sq ft (0.22 acres). Buildable Length = 120 ft - (25 ft + 10 ft) = 85 ft. Buildable Width = 80 ft - (7 ft + 7 ft) = 66 ft.
  3. 3 Intermediate Result: Buildable Area = 85 ft * 66 ft = 5,610 sq ft.
  4. 4 Final Result: The total lot area is 9,600 sq ft (0.22 acres), with a buildable area of 5,610 sq ft. This 5,610 sq ft represents the maximum footprint for a structure, directly impacting the potential market value and development density, which for this Austin lot could represent $438,000 of its total value based on buildable area metrics.

Source: HomeAdvisor · Last updated: April 2026

Frequently Asked Questions

How do I calculate my lot size in acres?
Multiply the lot width by the lot depth in feet to get square footage. Divide by 43,560 to convert to acres. A 100 x 200 foot lot is 20,000 square feet or 0.46 acres. For irregular shapes, use a lot survey or county GIS mapping tool.
What is the average lot size for a house?
The median lot size for a new single-family home is about 8,000-9,000 square feet (about 1/5 acre). Urban lots average 5,000-7,000 square feet, suburban lots 8,000-15,000 square feet, and rural lots are often 1 acre or more.
How do setbacks affect buildable area?
Setbacks are the required distances from property lines where you cannot build. Typical setbacks are 20-30 feet front, 5-10 feet sides, and 15-25 feet rear. On a 60x120 lot with standard setbacks, your buildable area may be only 40-50% of the total lot.

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