Topsoil Calculator

Topsoil formula

Cubic feet = Length (ft) x Width (ft) x Depth (in) / 12
Cubic yards = Cubic feet / 27
Tons = Cubic yards x 1.1
40 lb bags = Cubic feet / 0.75

Worked example

A 30 x 15 ft lawn area that needs 4 in of new topsoil: 30 x 15 x (4 / 12) = 150 cubic feet. 150 / 27 = 5.56 cubic yards. At 1.1 tons per yard that is about 6.1 tons, so order 6 yards in bulk. At $35 per yard the soil costs about $194 plus delivery.

In bags: 150 / 0.75 = 200 bags of 40 lb topsoil. At that quantity a bulk delivery is far cheaper and saves a lot of lifting.

Quick reference

How to calculate topsoil

Multiply the length by the width in feet to get the area, then multiply by the depth in feet (inches divided by 12) for cubic feet. Divide by 27 to convert to cubic yards, which is how bulk suppliers sell it. A 20 by 10 foot area at 6 inches deep is 100 cubic feet, or 3.7 cubic yards.

Suppliers often quote by the ton as well. Screened topsoil weighs roughly 1.1 tons per cubic yard when moderately moist. Soil settles 10 to 20 percent after it is spread and watered, so order a little extra if the final grade matters.

How deep should topsoil be?

For a new lawn, spread 4 to 6 inches of topsoil over the graded subsoil before seeding or laying sod. For vegetable gardens and raised beds, 8 to 12 inches gives roots plenty of room. To top-dress a thin lawn, rake in no more than 1/2 inch at a time so the grass can grow through it.

Bagged topsoil makes sense for a few small beds or planters. Above about one cubic yard (36 bags), bulk delivery costs less and arrives in one trip. A full-size pickup can carry about one cubic yard of dry topsoil, but that is close to its payload limit.

Key facts

• One cubic yard of topsoil weighs about 2,000 to 2,200 lb dry and can reach 3,000 lb when saturated.
• One cubic yard covers 162 sq ft at 2 in deep, 81 sq ft at 4 in, and 54 sq ft at 6 in.
• A 40 lb bag of topsoil holds about 0.75 cubic feet, so 36 bags make one cubic yard.
• A new lawn from seed or sod needs at least 4 to 6 in of good topsoil for healthy roots.
• Top-dressing an existing lawn uses only 1/4 to 1/2 in of screened soil or compost per application.

Frequently asked questions

Sources and references

• •Lawn Establishment (topsoil depth for new turf) (Penn State Extension)
• •Seeding and sodding home lawns (University of Minnesota Extension)
• •How to Use Compost in Gardens and Landscapes (EM 9308), calculating soil volume by area and depth (Oregon State University Extension)