Parking Lot Capacity Calculator
Estimate how many cars a parking lot holds — from its total area and the space each car needs including aisles, or by laying out rows on a rectangular lot at 90°, 60°, 45° or 30° — plus the lot size needed for a number of cars and the ADA accessible-space minimum.
How it works
Area method: spaces = ⌊lot area × efficiency ÷ area per space⌋ · Layout method at angle θ: stall depth d = L·sin θ + W·cos θ, width along the aisle w = W ÷ sin θ; bay = 2d + aisle; rows = 2 × ⌊lot width ÷ bay⌋ (+1 if a single row and aisle still fit); spaces per row = ⌊(row length − 2 × end aisle − (L·cos θ + W·sin θ)) ÷ w⌋ + 1 · Lot needed = cars × area per space ÷ efficiency
A single 9 × 18 ft stall is only 162 ft², but each car also needs a share of the drive aisle, so planners budget roughly 300–350 ft² (28–33 m²) per space across a whole lot. The area method multiplies the lot by an efficiency factor for entrances, islands, landscaping and setbacks, then divides by that allowance — quick, and good for a first estimate or a parking-ratio check. The layout method draws the lot instead: it fits double-loaded bays (a row of stalls, a drive aisle, another row) across the lot, takes out a cross aisle at each end of the rows, and counts how many stalls fit along each row at the angle you choose. It tries the rows both ways and keeps the better one. Ninety-degree stalls with a 24 ft two-way aisle usually fit the most cars; 60° and 45° stalls need narrower one-way aisles and are easier to pull into but lose space at the row ends. Every lot also needs accessible spaces: under the 2010 ADA Standards a lot of 76–100 spaces needs at least 4, and one in six of them must be van-accessible.
Worked example
A 30,000 ft² lot that is 90% usable gives 27,000 ft² of parkable area. At 325 ft² per standard 90° space that is ⌊27,000 ÷ 325⌋ = 83 spaces, of which the ADA requires at least 4 accessible (one van-accessible). Laid out instead as a 200 × 150 ft lot with 9 × 18 ft stalls at 90°: each bay is 18 + 24 + 18 = 60 ft, so 2 bays fit across 150 ft (4 rows, 30 ft spare). After a 24 ft cross aisle at each end, each row is 152 ft long and holds ⌊152 ÷ 9⌋ = 16 stalls, for 4 × 16 = 64 spaces — 469 ft² per space, because a lot that size wastes its spare strip. Turned the other way, the rows run along the 150 ft side, 3 bays fit across 200 ft and 6 rows × 11 stalls = 66 spaces, which the calculator picks.
Sources: ADA.gov — Restriping parking spaces (2010 ADA Standards, table 208.2)
Frequently asked questions
Why is a space 325 ft² when a car is much smaller?
The 325 ft² includes the stall itself plus the car’s share of the drive aisle needed to reach it. A 9 × 18 ft stall is 162 ft²; the rest is manoeuvring room, which is why real lots need far more area than the cars alone.
What angle parking fits the most cars?
Ninety-degree parking with a two-way aisle is usually the most efficient. Angled parking is easier to enter and works with narrower one-way aisles, but every row loses a triangle of space at its ends. Use Lot dimensions to see your lot at all four angles side by side.
How many accessible spaces do I need?
Under the 2010 ADA Standards (table 208.2): 1 for up to 25 spaces, 2 for 26–50, 3 for 51–75, 4 for 76–100, then one more per 50 up to 200 and per 100 up to 500, 2% of the total for 501–1,000, and 20 plus 1 per 100 over 1,000. At least one in six accessible spaces must be van-accessible. Local codes outside the US set their own minimums.
How big a lot do I need for 100 cars?
At 325 ft² per space and 90% usable, about 100 × 325 ÷ 0.9 = 36,100 ft², or 0.83 acres (3,354 m²). Choose Cars → lot size to try other allowances.
What is a parking ratio?
The number of spaces per 1,000 ft² of floor area or land. Zoning codes often require a ratio for each use, for example 3 to 5 spaces per 1,000 ft² of retail floor space. The calculator shows the ratio for the lot itself.
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This calculator is for educational purposes. Double-check important results before acting on them.