The Building Coverage Calculator is a tool used by architects, planners, and developers to determine the percentage of land on a plot that is covered by buildings and other covered structures. This calculation is crucial in land-use planning, especially when adhering to zoning regulations that dictate the allowable building coverage ratio (BCR) for specific land types. The Building Coverage Calculator helps ensure that projects meet local building codes and zoning restrictions, avoiding fines or the need for project redesign.
The tool calculates the ratio of the building footprint and other covered structures (such as garages and sheds) to the total buildable area of the plot. This allows property developers to assess whether their building plan is within acceptable limits and helps balance the need for green space, stormwater management, and other considerations important in urban planning.
Formula for Building Coverage Calculation
The formula for calculating the Building Coverage Ratio (BCR) is:
Building Coverage Ratio (BCR) = [(Building Footprint Area + Covered Ancillary Structures) / (Total Plot Area - Non-Buildable Areas)] * 100
Where:
- Building Footprint Area is the area of the main building that touches the ground. This is the horizontal area that the main structure occupies on the land plot.
- Covered Ancillary Structures include additional structures such as garages, sheds, porches, covered walkways, or any other roofed areas built on the plot.
The total area of these structures can be broken down further as:
Ancillary Structures = Garage Area + Covered Walkway Area + Storage Shed Area + Other Covered Structures
- Total Plot Area is the full area of the land on which the building and other structures are located.
- Non-Buildable Areas refer to sections of the plot that cannot be built on due to zoning laws, easements, protected natural areas, or other restrictions, such as wetlands, utility easements, or mandated green spaces.
This formula calculates the percentage of the plot that is covered by the building and other roofed structures, giving a clear indication of how much of the land is developed versus open or green space.
For example, if the building footprint is 5,000 square feet, ancillary structures cover 500 square feet, and the total plot size is 20,000 square feet with 2,000 square feet classified as non-buildable, the building coverage ratio would be:
Building Coverage Ratio = [(5,000 + 500) / (20,000 - 2,000)] * 100
Building Coverage Ratio = [5,500 / 18,000] * 100 ≈ 30.56%
This means that approximately 30.56% of the buildable land is covered by structures.
Quick Reference Table
Below is a quick reference table that helps users estimate building coverage ratios based on different plot areas, building footprints, and ancillary structures:
| Building Footprint Area (sq ft) | Ancillary Structures Area (sq ft) | Total Plot Area (sq ft) | Non-Buildable Areas (sq ft) | Building Coverage Ratio (%) |
|---|---|---|---|---|
| 2,000 | 300 | 10,000 | 1,000 | 25.29% |
| 3,500 | 400 | 15,000 | 2,000 | 27.71% |
| 5,000 | 500 | 20,000 | 2,000 | 30.56% |
| 7,000 | 700 | 30,000 | 3,000 | 29.90% |
| 10,000 | 1,000 | 40,000 | 5,000 | 28.57% |
This table is a useful resource for quickly assessing potential coverage ratios without needing to calculate each scenario individually. It helps developers and planners ensure that their designs comply with zoning rules while maximizing land use efficiently.
Example of Building Coverage Calculation
Let’s walk through an example to understand how the Building Coverage Calculator works.
Imagine you are a developer working on a residential project. You have a plot of land that is 30,000 square feet in total, but 3,000 square feet of this area is designated as non-buildable due to environmental protection regulations. The building footprint of the house is 7,000 square feet, and there are additional covered structures—a garage (600 square feet) and a porch (100 square feet)—making up a total ancillary structure area of 700 square feet.
Step 1: First, calculate the total area covered by buildings and structures:
Total Covered Area = Building Footprint Area + Ancillary Structures Area
Total Covered Area = 7,000 + 700 = 7,700 square feet
Step 2: Subtract the non-buildable areas from the total plot area to find the buildable land:
Buildable Plot Area = Total Plot Area - Non-Buildable Areas
Buildable Plot Area = 30,000 - 3,000 = 27,000 square feet
Step 3: Now, calculate the Building Coverage Ratio (BCR):
Building Coverage Ratio = (7,700 / 27,000) * 100
Building Coverage Ratio ≈ 28.52%
This means that 28.52% of the buildable area is cover by the house and other covered structures. This ratio will help determine whether the design meets zoning regulations and whether more or less building area can be add within allowable limits.
Most Common FAQs
A "good" building coverage ratio varies by region and zoning regulations. In urban areas, higher building coverage ratios (up to 60-70%) may be acceptable due to limited land. In suburban or rural areas, ratios below 30% are often preferr to maintain green spaces and promote low-density development.
To reduce your building coverage ratio, you can either reduce the size of your building footprint or minimize the number of covered ancillary structures like garages or sheds. Alternatively, you can increase the size of the plot, which will decrease the ratio.
Non-buildable areas are exclude because they cannot be develop due to zoning restrictions, environmental protections, or other legal factors. Excluding these areas ensures that the calculation focuses on the portion of the land that can legally support structures.