Calculate cubic yards and bags of compost for top-dressing a lawn, amending garden beds, or mixing raised-bed soil.
Compost goes on much thinner than mulch or topsoil, so the depth you choose matters more than anything else. A quarter inch over a lawn and three inches worked into a vegetable bed are very different orders. Pick the application below, measure the area, and the calculator converts it to cubic yards and bags.
Cubic Yards = (Length × Width × Depth in inches ÷ 12) ÷ 27(50 × 40 × 0.021) ÷ 27 = 1.54 cubic yards
| Application | Depth | Per 1,000 Sq Ft |
|---|---|---|
| Lawn top-dressing | ¼ inch | ≈ 0.8 cu yd |
| Heavier lawn top-dressing / after aeration | ½ inch | ≈ 1.5 cu yd |
| Annual garden bed refresh | 1 inch | ≈ 3.1 cu yd |
| New garden bed (tilled into top 6–8″) | 2–3 inches | ≈ 6–9 cu yd |
For lawns, rake the compost into the turf so the grass blades stay visible. Applying compost right after core aeration works it into the holes and gets it to the roots faster. For new beds, spread the compost and then till or fork it into the existing soil rather than leaving it on top.
Raised beds shouldn't be filled with pure compost, which is too rich and settles heavily as it breaks down. A common mix is about 60% topsoil and 40% compost, or up to 50/50 for vegetables. Calculate the bed's full volume with depth equal to the bed height, then multiply by your compost percentage. For example, a 4 × 8 ft bed, 12 inches deep, holds 32 cubic feet, so a 40% mix needs about 13 cubic feet of compost. Use the topsoil calculator for the rest.
Bagged compost is typically sold in 1 cubic foot bags, or in 40 lb bags of about 0.75 cubic feet. One cubic yard equals 27 cubic feet, which is 27 one-cubic-foot bags or 36 forty-pound bags. For anything over about one yard, bulk compost from a landscape yard or municipal composting program is usually far cheaper per yard.
| Source | Typical Cost |
|---|---|
| Municipal compost program | Free–$30 per cu yd |
| Bulk compost (landscape yard) | $30–$70 per cu yd |
| Bagged compost (1 cu ft) | $5–$12 per bag |
| Delivery | $50–$150 per load |
Finished compost should smell earthy, not sour or like ammonia, and have no recognizable food scraps. If you're buying in bulk, ask whether it has been screened and whether it's tested for contaminants, especially if you'll use it on edible crops.