Urban Planning Area Units
Blocks, Lots, and Density Measures
Learn Planning UnitsUrban planners, developers, and zoning officials use specialized area measurements to regulate development, calculate density, and manage city growth. Understanding these units—from city blocks to floor area ratios—helps interpret zoning codes and development plans.
City Block Sizes
"City block" varies significantly by city:
| City | Typical Block Size | Area |
|---|---|---|
| Manhattan (standard) | 250' × 900' (N-S) or 250' × 250' (E-W) | 5.7 acres |
| Portland, OR | 200' × 200' | 0.92 acres |
| Chicago (standard) | 330' × 660' | 5.0 acres |
| Salt Lake City | 660' × 660' | 10 acres |
| Barcelona (Eixample) | 113m × 113m | 1.28 hectares |
| Melbourne CBD | 100m × 200m | 2.0 hectares |
Note: Blocks often vary within the same city.
Lot Size Standards
US Residential Zoning
| Zone Type | Typical Minimum Lot | Area |
|---|---|---|
| High-density urban | 2,000-3,000 sq ft | 0.05-0.07 acres |
| Urban residential | 5,000-6,000 sq ft | 0.11-0.14 acres |
| Suburban (standard) | 7,000-10,000 sq ft | 0.16-0.23 acres |
| Suburban (larger) | 0.25-0.5 acres | 10,890-21,780 sq ft |
| Semi-rural | 1-2 acres | 43,560-87,120 sq ft |
| Rural residential | 5-10 acres | 217,800-435,600 sq ft |
Floor Area Ratio (FAR)
FAR controls building size relative to lot size:
FAR Calculation
FAR = Total building floor area ÷ Lot area
FAR Examples
| FAR | 10,000 sq ft lot allows | Typical Use |
|---|---|---|
| 0.5 | 5,000 sq ft building | Single-family suburban |
| 1.0 | 10,000 sq ft building | Low-rise residential |
| 2.0 | 20,000 sq ft building | Mid-rise mixed use |
| 5.0 | 50,000 sq ft building | Urban commercial |
| 10.0 | 100,000 sq ft building | Downtown high-rise |
| 15.0+ | 150,000+ sq ft building | Dense urban core |
Density Measurements
Residential Density
| Density Type | Units per Acre | Units per Hectare |
|---|---|---|
| Rural | 0.1-1 | 0.25-2.5 |
| Suburban (low) | 1-4 | 2.5-10 |
| Suburban (standard) | 4-8 | 10-20 |
| Urban (low-rise) | 15-30 | 37-74 |
| Urban (mid-rise) | 30-75 | 74-185 |
| Urban (high-rise) | 75-200+ | 185-500+ |
Population Density
- Low density: <5,000 people/sq mile
- Medium density: 5,000-15,000/sq mile
- High density: 15,000-50,000/sq mile
- Very high: >50,000/sq mile
Commercial/Industrial Units
Office Space
- Per employee: 150-300 sq ft (14-28 sq m) typical
- Post-COVID trend: 200-400 sq ft per employee
Retail Space
- Small retail: 1,000-5,000 sq ft (93-465 sq m)
- Big box: 50,000-200,000 sq ft (4,645-18,580 sq m)
Industrial/Warehouse
- Small: 10,000-50,000 sq ft
- Medium: 50,000-200,000 sq ft
- Large distribution: 500,000-1,000,000+ sq ft
Lot Coverage and Open Space
Lot Coverage Ratio
Lot coverage = Building footprint ÷ Lot area
| Zone Type | Typical Max Coverage |
|---|---|
| Single-family residential | 30-50% |
| Multi-family residential | 50-70% |
| Commercial | 70-90% |
| Industrial | 50-80% |
Open Space Requirements
Many codes require minimum open space:
- Private open space: 60-100 sq ft per unit
- Common open space: 100-200 sq ft per unit
- Parks standard: 10 acres per 1,000 residents
Conclusion
Urban planning uses specialized area measurements to control development density and form. Floor Area Ratio (FAR) limits total building size relative to lot size. Density measures units or people per acre/hectare. Understanding these metrics helps interpret zoning regulations and development potential—whether you're a developer, homeowner, or community member.