How Much Soil Do You Need?
The formula is simple: Cubic Feet = Length × Width × (Depth in inches ÷ 12). Then divide by 27 to get cubic yards. Our calculator also tells you how many bags to buy — whether you're picking up 1 cu ft or 2 cu ft bags from the store.
Best raised bed mix: A great all-purpose raised bed soil is 60% topsoil, 30% compost, and 10% potting mix (or perlite for drainage). This gives roots plenty of nutrients, good drainage, and moisture retention.
Soil Types Explained
Topsoil is the top 2–8 inches of native soil. It's dense and heavy, great for filling large areas or leveling lawns. Not ideal alone for raised beds because it can compact and drain poorly.
Potting Mix is lightweight and formulated for containers and raised beds. It drains well, holds moisture, and is usually sterile (no weed seeds). More expensive per cubic foot than topsoil.
Compost is decomposed organic matter — the best natural fertilizer. Adding 2–4 inches of compost annually improves any soil. It adds nutrients, improves drainage in clay soils, and helps sandy soils retain moisture.
- Lawn top-dressing: Apply 1/4 to 1/2 inch of compost across your lawn in fall or spring.
- New raised beds: Fill completely with potting mix or a topsoil/compost blend to 10–12 inches deep.
- Existing beds: Add 2–3 inches of compost each season to replenish nutrients.
Pro tip: Soil settles 10–15% after watering. Add 10–15% more than your calculated amount so the bed stays full after the first few waterings.