Compost Calculator

At 1 inch deep you need about 0.083 cubic feet per square foot — one cubic yard covers roughly 325 square feet. At the 2 inches typical for amending a bed, a yard covers about 160 square feet.

Not on its own. Pure compost holds too much water, settles heavily and can be too high in salts and nutrients for seedlings. A common mix is 50 to 60% topsoil, 30 to 40% compost and 10% aeration material such as perlite or coarse sand.

A quarter to half an inch, raked in so the grass blades still show through. Any thicker and you risk smothering the lawn. Aerating first lets the compost fall into the holes where it does the most good.

Measure the length and width in feet at the widest points and multiply them. For an irregular bed, break it into rectangles, circles and triangles, calculate each one separately and add the results together. Rounding up slightly is safer than rounding down.

Bulk is almost always cheaper per cubic yard once you need more than about 1 cubic yard — roughly 27 bags. Bags win when you need a small amount, have nowhere to dump a pile, or want to spread the job over several weekends.

A half-ton pickup can usually carry about 1 cubic yard of light material like mulch, but only around half a cubic yard of wet soil or gravel because of the weight. Check the weight figure above against your vehicle's payload rating before you load up.