Site Coverage Calculator

Calculate lot coverage percentage and open spaces.

Zoning
1

Design Parameters

Lot Area must be entered.

Quick Presets

Suburban Single Family Residence
Standard suburban lot rules.

Calculated Outputs

Building Footprint Coverage % of Lot
0.0
Total Impervious Coverage % of Lot
0.0
Open Green Space
1.0 m²

Site Metrics

Building Coverage 0.0% / 100.0%
Impervious Area 0.0% / 100.0%

Understanding Building Coverage & Impervious Ratios

Site coverage rules limit building sizes to maintain soil drainage, runoff basins, and landscape spacing.

Our Site Coverage Calculator evaluates footprint building coverages, total impervious surfaces, and open green space margins to ensure compliance with subdivision regulations.

Lot Coverage Illustration Visual showing building footprint vs. landscaped space.

Formulas and Definitions

Building footprint coverage measures only the percentage of the lot occupied by the main buildings. Total impervious coverage adds all paved hardscapes (such as concrete driveways, sidewalks, and patios) that block water infiltration into the soil.

Building Coverage Ratio (%) = (Building Footprint ÷ Lot Area) × 100
Total Impervious Coverage (%) = ((Building Footprint + Paved Hardscape) ÷ Lot Area) × 100
Example Lot Coverage Audit:

1. Lot Area: 2,000 m².

2. Building Footprint Area: 600 m².

3. Paved Hardscape/Driveway: 400 m².

4. Building Footprint Coverage: (600m² ÷ 2,000m²) × 100 = 30.0%.

5. Total Impervious Coverage: ((600m² + 400m²) ÷ 2,000m²) × 100 = (1000m² ÷ 2,000m²) × 100 = 50.0%.

6. Open Green Space: 2,000m² - (600m² + 400m²) = 1,000 m² (50.0% of the lot).

Result: The site has 30% building coverage and 50% total impervious coverage, leaving 1000 m² of green space.
Warning: Zoning bylaws, setback requirements, parking ratios, and buildable envelopes vary widely by municipality and jurisdiction. Always verify calculations against the local zoning ordinance and consult with a municipal planner or design professional before submitting development plans.

Environmental Impact of Impervious Coverages

Impervious surfaces prevent rainwater from absorbing naturally into the ground, leading to increased stormwater runoff. High runoff rates overload municipal storm sewers and cause local flooding. For this reason, modern zoning codes enforce strict caps on total impervious coverage and encourage green infrastructures like permeable pavers and bioswales.

Frequently asked questions

Does deck area count towards lot coverage?

Uncovered elevated decks are typically excluded from building coverage but are counted towards impervious surface coverage in zoning codes.

What is a typical building coverage limit?

Typical suburban residential zoning limits building footprint coverage to 30% or 40% of the total lot area, while commercial zones may allow 70% or higher.

Is grass considered pervious or impervious?

Grass, gardens, and unpaved soil are considered 100% pervious because they allow rainfall to drain directly into the ground.