Open Space Requirement Calculator

Plan outdoor space and setbacks with full confidence. See deficits instantly, then refine coverage assumptions. Make compliance decisions faster with transparent calculations every time.

Calculator Inputs
Choose the unit used in all area fields.
Gross parcel area before exclusions.
Easements, water bodies, steep slopes, setbacks.
Ground coverage by the structure.
Driveways, patios, paved yards, hardscape.
Used to estimate total floor area.
Rule: required = net site × ratio.
If 1.20, landscaped space counts 20% more.
Splits required open space into common vs private.
When enabled, the calculator compares ratio method vs per-unit method, then uses the stricter result.
Only used when the per-unit method is enabled.
Rule: required = units × per-unit value.
Formula used
  • Net Site Area = Site Area − Excluded Area
  • Existing Open Space = Net Site Area − (Building Footprint + Other Impervious)
  • Required (Ratio) = Net Site Area × (Required Ratio ÷ 100)
  • Required (Per-Unit) = Dwelling Units × Open Space per Unit
  • Required Base = max(Required Ratio, Required Per-Unit)
  • Adjusted Required = Required Base ÷ Landscape Factor
  • Provided % = (Existing Open Space ÷ Net Site Area) × 100
How to use
  1. Enter your site area and any excluded areas.
  2. Add building footprint and other impervious coverage.
  3. Set the required ratio from your local rulebook.
  4. Optionally enable per-unit checks for residential projects.
  5. Press Calculate to see compliance, deficit, and split targets.
Example data table
Scenario Site Excluded Footprint Impervious Ratio Units Per Unit Adjusted Required Existing Status
Mixed-use lot 2,000 150 600 250 20% — — 370 1,000 Compliant
Small infill 900 0 420 220 30% — — 270 260 Deficit
Residential block 4,800 300 1,350 900 25% 40 18 720 2,250 Compliant
Values shown are illustrative and use the same formulas as the calculator.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.