Topsoil Calculator

Multiply the bed's length by its width in feet, multiply by the fill depth in feet (inches divided by 12), and that is the cubic feet of soil; divide by 27 for cubic yards. A bed 4 by 8 feet filled 12 inches deep needs 32 cubic feet, about 1.19 cubic yards. University of Maryland Extension suggests filling with a mix of purchased topsoil and compost in roughly a 1:1 or 2:1 ratio, aiming for organic matter around 25 to 50 percent by volume - treat that as a starting guideline, not a fixed recipe.

A 4-by-8-foot bed has 32 square feet of surface. Filled 12 inches deep that is 32 cubic feet, about 1.19 cubic yards or roughly 32 one-cubic-foot bags. At an 8-inch fill it needs about 21 cubic feet (0.79 cubic yards), and at 6 inches about 16 cubic feet (0.59 cubic yards). Add a little extra if you expect the soil to settle after watering.

A cubic yard is 27 cubic feet, so it equals 27 one-cubic-foot bags, 18 one-and-a-half-cubic-foot bags, or about 14 two-cubic-foot bags. Bagged topsoil almost always costs more per cubic foot than bulk soil delivered by the yard, so bags make the most sense for jobs under roughly one cubic yard or where a truck cannot reach.

It depends on the use. For topdressing or leveling an established lawn, apply a thin layer of about a quarter to half an inch at a time (Penn State Extension). For a new lawn, 3 to 4 inches of topsoil worked into the ground gives roots room to establish. Planting beds want 6 to 12 inches of workable soil, and raised beds for vegetables want more still: Rutgers NJAES recommends a minimum 12-inch depth of imported topsoil, and University of Maryland Extension suggests 8 inches for leafy greens and 12 to 24 inches for deeper-rooted crops such as tomatoes and squash.

Topsoil is screened surface soil, sold in bulk for grading, lawns, and general planting. Garden soil and raised-bed mixes are topsoil already blended with compost and other organic matter, ready to plant into and lighter than bulk topsoil. Fill dirt is subsoil with little or no organic matter, used to build up low areas or backfill - it is not meant for growing. Compost is decomposed organic matter used to amend any of the others, not as a standalone growing medium. This calculator's soil-type option changes only the weight estimate, never the volume.

For a deep fill such as a new raised bed, yes - fresh soil is loose and drops noticeably once it is watered and worked, and organic matter continues to break down over the first season. Adding about 10 to 15 percent covers most cases. A thin topdressing layer barely settles, so no allowance is needed there. Use the optional settling field to raise the estimate; it is not a universal requirement.

Bulk screened topsoil is commonly estimated at roughly 1,800 to 2,500 pounds per cubic yard, heavier when wet or clay-rich and lighter when dry and sandy. A compost-amended garden or raised-bed mix is lighter, often around 1,000 to 1,700 pounds, while mineral fill dirt is heavier, often 2,000 to 3,000 pounds. There is no single standard density, so any weight shown here is an estimate for planning delivery and handling, not an exact figure.

Bulk soil, sold by the cubic yard and dropped by truck, is much cheaper per cubic foot and is the practical choice once you need more than about a cubic yard - a single 4-by-8 raised bed already reaches that point. Bags are worth it for small top-ups, containers, and sites a truck cannot access, or when you want a specific pre-blended mix. Suppliers usually set a minimum order and a delivery fee, so factor those in for smaller bulk jobs.