Topsoil Calculator

Topsoil volume formula

For a rectangle measured in feet, cubic feet = length × width × depth in inches ÷ 12. A triangle uses base × height ÷ 2 for its area. A circle uses π × (diameter ÷ 2)², so circular results are labeled approximate. A known-area zone starts directly from square feet.

The calculator adds the unrounded zone volumes, applies the exact extra percentage you entered, and divides by 27 to display cubic yards. It also converts the same combined volume to cubic meters and liters using the linked NIST unit references.

Worked example: 1,200 ft² at 4 inches

A 40-foot by 30-foot area is 1,200 square feet. Four inches is one third of a foot, so the volume is exactly 400 cubic feet. Divide by 27 to get about 14.815 cubic yards, or convert it to about 11.327 cubic meters, before adding an extra percentage.

Combine beds without losing the individual math

Different sections often have different depths. Enter each one as a named zone instead of averaging all measurements into one rectangle. The result lists every zone's area and volume, then uses the unrounded sum for the project total.

Use your own soil-mix recipe

The optional mix section divides the adjusted cubic-yard total among topsoil, compost, and another material. The three percentages must total exactly 100. The calculator does not choose a recipe or say which material fits a plant, site, drainage condition, or raised bed.

Bag count and bulk pricing

Package sizes vary, so bag calculations use only the cubic-foot volume printed on the package you enter. Whole bags round upward from the unrounded requirement, and the receipt shows purchased volume and calculated leftover. Bag cost uses that whole count.

Bulk cost multiplies the exact required cubic yards by your entered price per cubic yard, then adds the delivery charge you enter. It does not invent a supplier's half-yard increment, minimum order, tax, deposit, or delivery zone. Apply those terms to the copied receipt before ordering.

Planning boundaries

The extra percentage is a user-entered planning allowance. The tool does not assume universal settling, compaction, moisture, density, or weight, so it does not convert topsoil to tons. Irregular grades and excavation tolerances can change the quantity. Confirm the final measurements, product label, soil mix, and order rules with the supplier or project professional.

Input and rounding rules

Numeric fields accept unsigned complete ASCII decimals with up to six fractional digits. Signs, commas, fractions, exponent notation, Unicode digits, leading dots, trailing dots, and unit suffixes are rejected. Required dimensions must be greater than 0 and no more than 1,000,000; percentages may be 0 through 100.

Calculations use reduced BigInt rational values. Display values round half up only at the final step. Bag counts always round up from the unrounded project volume, so a rounded display value is never reused for purchasing math.