Project Inputs
Formula Used
- Base = Quantity × Ratio
- After shared = Base × (1 − Shared%)
- Final = After shared × (1 + Buffer%)
- Required = ceil(Final)
- Area/space ≈ W × (D + A/2)
- Avail area = Site × Parking%
- Spaces/level = floor(Avail×Eff / Area/space)
- Provided = Spaces/level × Levels
Ratios and geometry are planning assumptions. Confirm local codes, circulation, slopes, and fire access requirements during design development.
How to Use This Calculator
- Select a land use preset, then set the demand basis.
- Enter GFA, units, seats, or employees for your basis.
- Adjust shared parking reduction and buffer if applicable.
- Enter site area, parking availability, and number of levels.
- Pick a parking angle and review stall and aisle dimensions.
- Click Calculate to view results above the form.
- Export the results table to CSV or PDF when needed.
Balancing Demand and Site Capacity
Off-street parking planning begins by comparing required spaces to what the site can physically hold. This calculator estimates demand from your chosen basis, then estimates supply from available parking area, layout geometry, and levels. If the summary shows a deficit, treat it as an early warning to revise the program, add levels, or negotiate shared parking.
Interpreting Parking Ratios
Parking ratios are entered as “spaces per basis.” For example, 4.0 spaces per 1,000 ft² means a 25,000 ft² office yields about 100 spaces before adjustments. The shared reduction lowers demand when peak periods do not overlap, while the design buffer adds contingency. Together they convert a base estimate into a more buildable requirement.
Layout Efficiency and Module Area
Supply depends heavily on stall width, stall depth, aisle width, and an efficiency factor. The calculator uses a double-loaded module approximation: area per space ≈ W × (D + A/2). Tight aisles may improve count but can hurt maneuvering; wider aisles reduce count but improve circulation. Parking angle choices (45°, 60°, 90°) change module depth and aisle needs, which can shift capacity. The efficiency factor accounts for islands, ramps, fire lanes, and non-rectangular losses.
Multi-Level and Shared Parking Scenarios
When land is constrained, increasing levels multiplies spaces provided without changing the footprint. Use the “parking area available” percentage to remove building coverage, setbacks, and landscaping. For mixed-use projects, test several shared reduction values (for example 10–30%) and review how the rounded required spaces change. Document assumptions in your submittals, and keep a record for design changes.
Cost, Accessibility, and Reporting
Add a cost per space to produce a quick budget signal for lots or structured parking. If accessibility is enabled, the tool provides a minimum accessible count based on total spaces used for sizing, and targets for EV and bicycle spaces. Export CSV for spreadsheets and PDF for permitting packages and internal reviews. Use the view to align stakeholders quickly.
FAQs
1) What demand basis should I choose?
Use the basis that matches your parking schedule: floor area for offices and retail, units for housing and hotels, seats for dining and assembly, or employees for operational sites. Enter only the inputs required for that basis.
2) What does the efficiency factor represent?
Efficiency reduces theoretical capacity to account for drive aisles, islands, end caps, ramps, fire access, and irregular geometry. Start around 0.85 for clean rectangular lots, then lower it if your layout has constraints or complex circulation.
3) Are the stall and aisle defaults mandatory?
No. The defaults are planning assumptions that help you start quickly. Override dimensions to match your jurisdiction, vehicle mix, and design standards. Always verify turning, grading, drainage, and emergency access during detailed design.
4) How is the accessible minimum estimated?
When enabled, the tool applies a common step-based minimum by total spaces used for sizing and reports the resulting accessible count. Confirm exact accessible stall, aisle, and signage requirements with local regulations and project type.
5) How do I test shared parking scenarios?
Enter a shared parking reduction percentage and rerun several cases, such as 10%, 20%, and 30%. Compare the required rounded spaces and keep notes on the operating assumptions that justify each reduction for reviewers.
6) What should I export for approvals?
Use the PDF for submittals, plan reviews, and meeting packs because it captures the summary table cleanly. Use the CSV for internal spreadsheets, cost models, and sensitivity checks across multiple scenarios.
Example Data Table
| Scenario | Demand basis | Example input | Typical ratio | Estimated required spaces |
|---|---|---|---|---|
| Office building | GFA per 1,000 ft² | 25,000 ft² | 4.0 | ≈ 100 |
| Retail strip | GFA per 1,000 ft² | 12,000 ft² | 5.0 | ≈ 60 |
| Restaurant | Seats | 120 seats | 0.3333 (≈1 per 3 seats) | ≈ 40 |
Example values are illustrative. Replace with your local parking schedule.