Compost Calculator
Calculate compost volume needed and get a browns-to-greens ratio guide for your garden.
For a healthy compost pile, aim for a 30:1 carbon-to-nitrogen ratio.
Browns (carbon): dry leaves, straw, cardboard, wood chips
Greens (nitrogen): grass clippings, vegetable scraps, coffee grounds
Mix roughly 3 parts browns to 1 part greens by volume.
How the Compost Calculator Works
The calculator converts your garden area and desired compost depth into volume. Cubic feet = area × (depth in inches / 12). That figure is divided by 27 to get cubic yards — the standard unit used by bulk suppliers. For bagged compost, a standard 40-lb bag covers roughly 0.75 cubic feet, so the bag count is the cubic feet total divided by 0.75, rounded up. Weight is estimated at 800 lbs per cubic yard, a typical figure for finished compost. Unfinished compost may be slightly lighter but is not recommended as a topdressing since it can rob soil nitrogen as it continues to break down. For new raised beds, use 4–6 inches of compost mixed into the top 12 inches of native soil. For established beds, a 2–3 inch annual topdressing applied each spring is sufficient.