Parking ratio is a formula used to compare the number of parking spots available in a lot to the square footage of building space. Cities and municipalities normally have ratio requirements to ensure adequate parking space and safety for workers and guests. These vary by property type. For example, a retail center will generally have a higher parking ratio than an office development.

How to Perform a Standard Calculation

Generally, the ratio is calculated by dividing the number of vehicle parking spaces into the building's square footage, and expressing the result per 1,000 square feet. Take a retail plaza with 300 parking spots and 60,000 square feet of shopping space. To calculate the parking ratio, divide 300 by 60. The result is five parking spots for each 1,000 square feet of floor space in the plaza. It's that simple.

Why Does the Parking Ratio Matter?

Local government agencies will establish a parking ratio to ensure there is adequate parking to coincide with a new property development. As such, parking requirements will vary by building type. A general manufacturing plant may need only two or three spaces per 1,000 square feet, for example, whereas an office development may need five or six spaces. A city or county website is a good resource to find municipality parking requirements. Business developers or operators can contact a city or county office to get parking ratio requirements if they aren't published online.

Tenants have their own requirements based on the number of staff and visitors they need to accommodate at the building. For some tenants, a higher parking ratio is desirable and buildings with a good ration may command a higher rent.

Parking Ratio Must Comply with the ADA

The Americans with Disabilities Act includes provisions that businesses must allocate a portion of parking spots to handicapped drivers, including spaces that are at least 96 inches wide for van accessibility. As of 2018, for the first 100 total spots, every 25 spots must have a corresponding handicap spot. As the total spots increase, the portion required for handicap spots decreases. From 101 to 150 spots requires a fifth handicap space, and from 151 to 200 requires a sixth. Between 201 and 300 spots, a seventh spot is needed. From 301 to 400 spots dictates an eighth handicap space, and from 401 and 500 total spots, a ninth handicap spot is required.

Businesses that don't currently meet ADA parking requirements are expected to restripe and do so as soon as is reasonably possible.