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How Much Mulch Do I Need

The shortcut formula

Because one cubic yard holds 27 cubic feet and there are 12 inches in a foot, square feet multiplied by inches and divided by 324 gives cubic yards directly. That number is the most useful thing to know when ordering bulk mulch. For bags, divide cubic feet (area × inches ÷ 12) by the bag size printed on the bag, usually 2 or 3 cubic feet. The mulch calculator does both.

Measuring real beds

Garden beds are rarely neat rectangles. Break each one into simple shapes. For a kidney-shaped bed, two overlapping rectangles and a half circle get you within a few percent. For a circle around a tree, use 3.14 times radius squared, then subtract the trunk area if it is large. Long narrow borders are easiest measured as length times average width. Write every shape down; a sketch on paper prevents double counting.

Check what is already there

Most people are refreshing mulch, not starting from bare soil. Push a finger or trowel into the existing layer in several spots. If you have an inch of old mulch and want three inches, you need only two more. Ordering for the full depth on top of existing mulch is the most common reason people end up with a heap left over, and piling too much around plants can harm them.

Quantity table

Yards or bags

Below roughly one cubic yard, bags are usually simpler: you can carry them in a car, store leftovers neatly and buy them anywhere. Above two or three yards, bulk delivery tends to be cheaper even with a delivery fee. In between, compare with your local prices using the bags vs bulk calculator. Consider where a bulk pile will sit and whether rain might stain a driveway.

Coverage per bag

One 2 ft³ bag covers about 12 ft² at 2 inches, about 8 ft² at 3 inches and about 6 ft² at 4 inches. A 3 ft³ bag covers half again as much. Bag sizes vary, so read the label rather than assuming.

How mulch type changes the order

Fine shredded mulch knits together and settles slightly after watering, so a small extra helps. Large bark nuggets leave gaps, so many gardeners lay them a bit deeper for the same coverage. Rubber mulch is heavier and is often applied at different depths for play areas; see the rubber mulch guide. Stone used as mulch is calculated with the gravel tools instead.

Spreading tips

Keep mulch a few inches away from tree trunks and plant stems so bark stays dry. Rake evenly and check depth with a ruler in a few places as you go. Water lightly after spreading to help it settle. Spread in spring once soil has warmed, or in autumn to protect roots before winter.

Mulch around trees

For a tree ring, measure the radius from the trunk to the edge you want, square it and multiply by 3.14. Subtract a small circle at the trunk where mulch should not touch. Wide, shallow rings are kinder to trees than small, deep piles.

Metric beds

Metric equivalents for common bed sizes. The tonne figure uses a light 0.3 US tons per yard wood mulch density and varies widely with moisture:

Storing leftovers

Leftover bags keep well if stored flat and out of the sun. Bulk leftovers can sit under a breathable tarp; avoid sealing them airtight, which can make the mulch sour. Use leftovers for paths, tree rings or next spring's top-up.

Ordering checklist

Total area, existing depth, target depth, mulch type, bag size or bulk unit, delivery address and drop spot, tarp for driveway, and helpers for spreading day. With those written down, an order call takes two minutes.

Slopes and edges

On slopes, use shredded mulch that knits together, and consider a slightly thinner layer so it does not slide in heavy rain. A shallow trench edge along lawns, cut with a flat spade, holds mulch in place and gives a crisp line without buying edging. Account for the trench in your measurement only if you will fill it, which adds very little volume. Along walkways, keep mulch a little below the path surface so it does not wash onto it.

If your result lands between bag sizes or between half-yard increments, round up slightly. A few spare bags cover thin spots discovered while spreading and tidy edges after the first heavy rain shifts material.

Measure twice before ordering, especially for beds you only estimated by eye last year.

Worked example

Illustrative examples (2026-10-29), not quotes or guarantees.

Front beds: 30 × 4 ft + 12 × 6 ft = 192 ft². Existing mulch averages 1 in; target 3 in → add 2 in. 192 × 2 ÷ 324 ≈ 1.19 yd³ ≈ 16 bags of 2 ft³. Full 3 in from bare soil would have been about 24 bags.

FAQ

How many bags of mulch in a yard?

13.5 bags of 2 ft³; 9 bags of 3 ft³.

How much does a yard cover?

About 162 ft² at 2 in, 108 ft² at 3 in.

Should I remove old mulch?

Usually only if it is matted or excessive; otherwise top up.

Related: Mulch calculator · Mulch depth · Mulch types