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Building Coverage Ratio Calculator

Calculate the building coverage ratio (%) from site area and building footprint. Reverse-calculate the maximum buildable area from a zoning limit, with corner-lot relaxation explained.

Input

What to calculate

m²
m²
%

Result

Coverage ratio

50%

Within the allowed coverage ratio of 60%

Site area

150 m²

Building footprint

75 m²

Coverage ratio (limit)

60 %

ItemValue
Site area150 m²
Building footprint75 m²
Coverage ratio50 %
Buildable area at the allowed limit90 m²

Coverage ratio = building footprint ÷ site area × 100. The building footprint is the horizontal projected area of the building seen from directly above. For corner lots and other sites that meet conditions set by the local authority, the limit may be relaxed by 10% (corner-lot relaxation). Always confirm whether a relaxation applies and the exact figures with your municipality's city-planning rules and ordinances.

How it works

  • Building coverage ratio is found with "building footprint ÷ site area × 100". The building footprint is the horizontal projected area of the building seen from directly above (roughly the area enclosed by the centerlines of the first-floor exterior walls and columns).
  • In "Find the coverage ratio" mode, enter the site area and building footprint to display the coverage ratio (%). Enter the allowed coverage ratio limit as well, and the tool checks whether you are within or over the limit.
  • In "Find the buildable area" mode, enter the site area and the zoning coverage ratio to reverse-calculate the maximum buildable footprint (m²). Use it as a guide when searching for land or planning a floor layout.
  • The coverage ratio limit is set by city planning for each zoning district. On sites that meet conditions designated by the local authority, such as corner lots, a "corner-lot relaxation" raising the limit by 10% may apply.
  • Other relaxations exist as well, for example when building a fire-resistant structure within a fire-prevention district. Always confirm the figures and conditions that actually apply with your municipality's city-planning or building-guidance department.
  • Results from this tool are estimates based on general principles. For official decisions such as building confirmation applications or purchase contracts, rely on professionals and the latest information from the authorities.