Parking Lot Space Calculator
Estimate the number of parking spaces that fit in a rectangular parking lot based on lot dimensions, stall size, drive aisle width, and parking angle.
Formulas Used
Projected stall width along row (angled):
Effective Stall Width = Stall Width / sin(θ)
Projected stall depth perpendicular to row (angled):
Effective Stall Depth = Stall Depth × sin(θ) + Stall Width × cos(θ)
Module depth (two back-to-back rows + one drive aisle):
Module Depth = 2 × Effective Stall Depth + Aisle Width
Total rows:
Rows = (floor(Lot Width / Module Depth) × 2) + extra single row if space permits
Stalls per row:
Stalls per Row = floor(Lot Length / Effective Stall Width)
Adjusted spaces:
Spaces = floor(Total Rows × Stalls per Row × Efficiency Factor)
Parallel parking (0°): Stall depth runs along lot length; stall width runs along lot width.
Assumptions & References
- The lot is assumed to be a simple rectangle with no obstructions.
- Standard stall dimensions per ITE and ULI guidelines: 8.5 ft wide × 18 ft deep for 90° parking.
- Standard two-way drive aisle: 24 ft for 90° parking; narrower aisles (18–20 ft) are acceptable for 45°–60° one-way layouts.
- The efficiency factor (typically 80–90%) accounts for landscaping islands, pedestrian walkways, fire lanes, entrance/exit driveways, and irregular lot shapes.
- Angled parking formulas derived from geometric projection of stall dimensions onto lot axes (ITE Parking Generation Manual).
- Back-to-back double-loaded rows are assumed for maximum efficiency.
- Results are estimates; actual capacity may vary based on local zoning codes and ADA requirements (typically 1 accessible space per 25 total spaces).
- Reference: Urban Land Institute, Parking Requirements for Shopping Centers; ITE, Parking Generation, 5th ed.