How Much Peat Moss Is Needed to Amend 240 Square Feet?

Percent of Soil

• Peat moss, as a soil amendment, constitutes about a third of the soil volume. For example, if the soil is worked 6 inches deep mix a 2-inch layer of peat moss in as an amendment. Deeper cultivation requires a deeper layer of peat moss. Extremely deep cultivation of 18 inches requires at least 6 inches of peat moss. Common cultivation with garden tillers is between 6 and 8 inches requiring 2 to 2 1/2 inches of peat moss across the garden.

Making the Calculation

• Calculating the amount of peat moss necessary requires multiplying the area of the garden by the depth of peat moss. Convert the square footage of the garden into square inches by multiplying by 144. In this case the 240-square-foot garden translates to 34,560 square inches. Multiply this by the planned depth of the peat moss. If you plan on 2 inches of peat moss this garden would require 69,120 cubic inches of peat moss. Divide this by 1,728 to translate cubic inches to cubic feet. In our example, this would mean 40 cubic feet of peat moss is necessary to serve as a soil amendment for a 240-square-foot garden.

Buying Peat Moss

• Producers market peat moss in various sized packages. Divide the number of cubic feet of peat moss required by the amount of peat moss in a bag. For example, if the peat moss is purchased in 3 cu. ft. bags it would take slightly more than 13 bags to provide 2 inches of peat moss over a 240-square-foot garden.

Incorporating Peat Moss

• Gardeners commonly use a tiller to work the peat moss into the soil. Tillers use a gasoline engine to power rotating tines that breakup and mix the soil. Adjust the tiller to work to the desired depth. Other options include working the soil with a garden fork or shovel. Monitor how deep the fork is inserted into the ground to mix the soil and peat moss.