How to Calculate Topsoil
Measure your area in feet and decide on the depth. For amending existing garden beds, 2–4 inches is typical. For establishing a new lawn, 4–6 inches of quality topsoil is recommended. For raised beds, you'll need 8–12 inches. One cubic yard of topsoil covers about 108 square feet at 3 inches deep and weighs approximately 1.1 tons (2,200 lbs).
Topsoil vs Garden Soil vs Compost
Topsoil is screened natural soil ideal for filling and grading. Garden soil is topsoil blended with compost and fertilizer — better for planting but more expensive. Compost is fully decomposed organic matter used as an amendment. For best results, mix topsoil with 20–30% compost when building new garden beds.