Soil Calculator

How soil volume is calculated

Topsoil, compost, garden soil, and mulch are all sold by volume, and the math is identical for all of them — only the material changes:

Cubic feet = length (ft) × width (ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size (1, 1.5, or 2 cu ft), rounded up

One cubic yard covers about 27 sq ft a full 12 inches deep, 54 sq ft at 6 inches, or 108 sq ft at 3 inches. A standard 4 × 8 ft raised bed filled 12 inches deep needs exactly 32 cu ft — about 1.19 cubic yards, or 22 bags of 1.5 cu ft.

Depth guide: raised vegetable beds are usually filled 10–12 inches (the frame is often 11–12 in tall); topping up an existing bed takes 2–3 inches; amending a garden in place, 1–2 inches of compost worked in; filling low spots in a lawn, 1–4 inches of topsoil at a time so the grass can grow through.

Settling is real: loose soil and compost compact and decompose — a freshly filled bed can drop 10–20% in the first season. Ordering about 10% extra is standard practice, and leftover material keeps fine in a pile or bin. For bulk delivery, remember a cubic yard of moist topsoil weighs roughly a ton, so plan the drop spot accordingly.

Frequently asked questions

Bags or bulk? The crossover is around half a cubic yard. Below that, bags are cleaner and you pay for convenience; above it, bulk delivery is dramatically cheaper per cubic foot and one truck drop replaces dozens of car trips.

What's the raised-bed mix? A common recipe is 60% topsoil, 30% compost, and 10% aeration material (perlite/pumice). Run this calculator once for the total volume, then multiply by each share to split the order.

My bed isn't a rectangle. Round beds: use length = width = diameter and multiply the result by about 0.785. Triangles: use the bounding rectangle and halve the result.