| Scenario | Total site (sqm) | Deductions (sqm) | Existing public (sqm) | Proposed public (sqm) | Other public (sqm) | Population | Target ratio (%) | Target per-capita |
|---|---|---|---|---|---|---|---|---|
| Mixed-use block | 12,000 | 500 | 900 | 300 | 150 | 1,200 | 10 | 9 |
| Neighborhood renewal | 25,000 | 2,000 | 1,800 | 900 | 300 | 2,400 | 12 | 8 |
Net Public Space (sqm) = Existing + Proposed + Other
Public Space per Capita (sqm/person) = Net Public Space ÷ Population
Needed for per-capita (sqm) = max(0, (Target Per-Capita × Population) − Net Public Space)
Recommended addition (sqm) = max(Needed for ratio, Needed for per-capita)
- Choose your input unit and enter total site area.
- Add deductions to focus on the net site area.
- Enter existing, proposed, and other public space areas.
- Provide the population served and target benchmarks.
- Click Calculate to view results above.
- Use CSV or PDF exports for records and reviews.
Why public space ratio matters
Public space ratio expresses how much of a site is publicly accessible compared with the net site area. On construction and masterplanning projects it supports zoning checks, feasibility studies, and stakeholder review. A ratio also helps align design teams on minimum open space commitments early. It can be tracked across design stages to control scope creep and safeguard approvals.
Inputs that change the outcome
Use total site area for the parcel boundary, then subtract deductions such as setbacks, easements, watercourses, or reserved corridors to form the net site area. Public space should include spaces with legal access, clear edges, and defined maintenance responsibility. Population served must match the approval intent: residents, workers, or a combined catchment. Record the measurement method, such as GIS, CAD, or surveyed areas.
Interpreting ratio and per-capita together
A project can meet a percentage ratio yet still underperform per-capita provision if population is high. The calculator reports both indicators and shows compliance against targets you define. When results conflict, prioritize the stricter requirement or document the policy basis used. Per-capita is useful for comparing alternatives with different densities.
Worked example with numbers
Example inputs: Total 12,000 sqm, deductions 500 sqm, existing public 900 sqm, proposed 300 sqm, other public 150 sqm, population 1,200, targets 10% and 9 sqm/person. Net site is 11,500 sqm and net public space is 1,350 sqm. Ratio equals 11.74%, while per-capita equals 1.13 sqm/person. Additional public space needed to meet 9 sqm/person is 9,450 sqm.
Quality checks before exporting
Confirm areas are measured consistently from the same drawing revision. Avoid double-counting shared corridors and private amenity decks. If using square feet, verify the conversion to square meters in the outputs. Add notes on exclusions, access conditions, and population assumptions, then export CSV or PDF for audit trails.
1) How do I choose the population served?
Use the population definition required by your approving authority. For residential schemes, use projected residents. For employment sites, use peak workers. For mixed-use, document a combined catchment and state the source of assumptions.
2) Should private courtyards be counted as public space?
Only count spaces that are legally accessible to the public and remain accessible over time. Private amenity decks, resident-only courtyards, and controlled-access podiums usually do not qualify unless policy explicitly allows them.
3) Why does the calculator convert to square meters?
Standardizing results avoids unit confusion in reviews. If you enter square feet, the tool converts inputs using 1 sqft = 0.09290304 sqm and reports all KPIs in square meters and sqm/person.
4) What are typical targets for ratio and per-capita?
Targets vary by city, zoning, and project type. Some plans set a minimum site ratio, while others emphasize sqm/person. Enter the specific values from your local guidelines or project brief for defensible reporting.
5) How is additional public space needed calculated?
The tool computes the minimum public space required to meet your ratio target and your per-capita target, then reports the larger shortfall. This recommended addition helps ensure both requirements are satisfied simultaneously.
6) What if deductions make the net site area very small?
If net site area becomes zero or negative, the ratio is invalid. Reduce exclusions to only those permitted by policy, or verify parcel boundaries and easements. The calculator will warn you when net site area is not feasible.
7) Can I use this for phased construction?
Yes. Run the calculator per phase and for the ultimate build-out. Keep population and public space assumptions consistent across phases, and add notes describing which spaces are delivered when and how access is maintained.