Compost Top-Dress Calculator

Estimate compost for a shallow top-dressing layer.

Calculate a compost layer, not the whole bed

This tool treats the entered depth as the thickness of the compost layer. A 2-inch top-dress over 80 square feet is very different from filling an entire bed to 12 inches.

Worked example

For 20 × 4 feet with a 2-inch layer: 20 × 4 × (2 ÷ 12) = 13.33 cubic feet, about 0.49 cubic yard.

Measure only the area you will cover

Subtract paths, permanent edging or uncovered planting holes when they make a meaningful difference to the material order.

Keep top-dressing depth separate from bed depth

A one- or two-inch compost layer is a surface amendment, not a full refill. This version emphasizes the layer so an established bed is not accidentally calculated as if all soil were being replaced.