How Much Gravel & Sand Should Go in a Patio Hole?

Measure the Site

• You need to know the site's exact dimensions in order to figure the amount of materials to purchase for a patio. Use a tape measure to measure the length and width of the site, and multiply these figures. For example, a 10-by-10 foot patio is 100 square feet.

Determine the Depth

• Depth is a key factor in building a solid foundation. The gravel base must be thick enough to support the pavement under normal wear and tear, and to absorb tension when underground moisture freezes in winter. The foundation should also begin below the frost line to help prevent frost heave damage. For patios, a 6- to 8-inch-thick layer of gravel is standard. If your yard has poor drainage, the foundation should be a few inches deeper. Calculate the total depth of the site by adding the thickness of the gravel base to 1 inch of grit sand and half the thickness of your paving material.

Calculate Gravel

• Once you determine the appropriate thickness of the gravel base you need to calculate the cubic feet. A 6-inch thick base is half of a foot. Multiply the square footage by one-half to figure the cubic feet of the base. For instance, a 100-square foot patio with a base 6 inches thick requires 50-cubic feet of gravel. As most places sell gravel in cubic yards, divide the cubic feet by 27 to calculate the amount in cubic yards. It's advantageous to add 5 percent on to this amount for spillage or any slight variation in the patio's actual size.

Calculate Sand

• The sand bed that goes over the gravel is typically 1 to 1 ½ inches thick. When calculating sand, account for the fact that some will fall between the narrow crevices in the gravel. Rather than calculating based on the 1-inch layer, determine the amount of sand needed by simply ordering one third the amount of gravel in cubic yards.