How much mulch do I need for a bed?

Mulch is one of the few materials where the bag count and the bulk volume disagree in a way that costs real money: a yard of mulch is 13.5 standard two-cubic-foot bags, and the same yard delivered loose is usually cheaper than five of those bags. This calculator gives both numbers so you can choose.

Bed length (ft)

Bed width (ft)

Depth (in)

2-3 in for maintenance, 3-4 in for a new bed.

Bag size 2 cubic feet (standard bag)3 cubic feet (large bag)1.5 cubic feet (small bag)

Mulch needed

0.74yd³

Bags to buy 10 bagsCubic feet 20.0 ft³

Assumes a rectangular bed and a settled depth. Irregular or curved beds should be measured as an average width, which typically over-estimates by 5-10%; treat the bag count as a floor, not a ceiling.

Depth is the whole calculation. Two inches is maintenance — enough to top up a bed that has broken down over a season. Three inches is the standard for a bed that needs suppressing weeds, and four inches is for a new bed over bare soil or fabric. More than four inches starts to hurt plants: it holds water against stems and roots instead of letting the surface breathe.

Beds are rarely rectangles, so measure the average width rather than the widest point, and split an L-shaped bed into two rectangles. Mulch settles by roughly a third over a season as it breaks down, which is why the same bed wants topping up every spring rather than every few years.

How the calculation works

Cubic feet = length (ft) × width (ft) × depth (in) ÷ 12. Cubic yards = cubic feet ÷ 27. Bags = cubic feet ÷ the volume of one bag, rounded up, because you cannot buy a partial bag.

One cubic yard is 27 cubic feet, so at two cubic feet per bag a yard is 13.5 bags — round to 14 if you are buying bags.

• The bed is a rectangle or can be approximated by one; irregular beds should be split into rectangles and summed.
• Depth is the settled depth of mulch, not the fluffed volume from the bag, which is looser than it looks and settles quickly.
• No allowance is made for existing mulch that will remain in place, and no waste factor is applied because mulch has no cutting loss — the leftover goes in the next bed.
• Bags are assumed to be labelled in cubic feet, which is the US standard; some are sold by dry quarts, where 25 quarts is roughly one cubic foot.

Sources: 1 cubic yard = 27 cubic feet; standard US bag = 2 cubic feet; Bed depth guidance: 2-3 in established beds, 3-4 in new beds (extension-service guidance)

Worked examples

Questions

How many bags of mulch are in a cubic yard?

13.5 bags of 2 cubic feet, 9 bags of 3 cubic feet, or 18 bags of 1.5 cubic feet. Suppliers usually round up, so 14 standard bags is a safe equivalence.

How deep should mulch be?

Two to three inches for most beds, four for a new planting over bare soil. Deeper than four inches can smother shallow roots and hold moisture against stems.

How many square feet does a yard of mulch cover?

At 3 inches, about 108 sq ft. At 2 inches, 162 sq ft; at 4 inches, 81 sq ft. The coverage falls as depth rises, in direct proportion.

Do I need to remove old mulch first?

Not if it has broken down and the total depth stays under four inches. If the old layer is still intact and matted, rake it to break the surface before adding more, or the new mulch will shed water.

Is bagged or bulk mulch cheaper?

Bulk is almost always cheaper per cubic foot once you need more than about two yards, but only if the delivery charge is reasonable and you have somewhere to dump it.

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Written and maintained by Sam Winters. Last updated 2026-11-04. Every figure is computed in your browser; nothing you enter is sent anywhere. Found an error? Tell me — accuracy reports get fixed first.