Mulch Calculator

Mulch and gravel volume follows the same bulk-material formula used for topsoil and stone: length × width × depth. US mode converts depth from inches to feet before multiplying, then reports cubic yards and bag counts based on bag size in cubic feet. Metric mode uses meters for length and width, centimeters for depth, and reports cubic meters plus liters per bag. The same physical bed produces the same volume regardless of which unit system you choose.

Landscape mulch is typically spread 2–4 inches (5–10 cm) deep. Three inches is a common target for weed suppression and moisture retention without smothering plant crowns. One cubic yard covers roughly 108 square feet at 3 inches deep — a handy rule when comparing bulk delivery quotes to bagged product at the garden center.

Bag counts round up because partial bags are not sold. If your project needs 9.2 bags at 2 cubic feet each, buy 10. Leftover mulch stores in a dry corner of the yard for touch-ups after settling. Bulk cubic yards cost less per unit on large beds; bags are easier for small projects, steep slopes, and tight vehicle access.

Do not pile mulch against tree trunks — leave a few inches clear to avoid bark rot and pest entry. Refresh annually as organic mulch decomposes; inorganic gravel rarely needs topping except after erosion. Switch the unit toggle before entering dimensions so labels match your tape measure.

Irregular beds can be split into rectangles, calculated separately, and summed. Curved edges add only a small margin if you approximate with straight segments. For circular beds, use a dedicated circle area tool first, then treat depth the same way as a rectangular bed.

Gravel paths and decorative rock use identical math — only depth recommendations differ. Path gravel often runs 2–3 inches deep; driveways need engineering specs beyond this simple volume estimate. Always confirm local supplier coverage rates on the product label.

Organic mulch compresses under rain and foot traffic — remeasure depth the following season rather than assuming last year's thickness remains. Dyed mulch may fade; natural bark weathers to gray without changing volume much until it decomposes into soil.

Worked example with default inputs: a 20 ft × 4 ft bed at 3 inches deep equals 20 cubic feet (20 × 4 × 0.25 ft depth), or about 0.74 cubic yards. At 2 cu ft per bag, that is 10 bags. Metric equivalents after toggling units would use the same volume expressed in cubic meters and liters.