Calculators / Mulch
Sold by the bag or yard
Mulch calculator
Measure the bed, pick a depth, and get the number of bags to put in the cart — plus the point where a bulk delivery starts costing less than bagged.
How deep, by project
| Project | Depth | Notes |
|---|---|---|
| Topping up existing mulch | 1–2 in | Only enough to restore colour and cover. Do not keep stacking on top of old mulch year after year. |
| Standard bed, established plants | 3 in | The default. Blocks light to weed seeds while still letting rain and air through. |
| Weed suppression on bare ground | 4 in | Use with a hoed, weed-free surface. Deeper than this and you are building an anaerobic mat. |
| Around tree trunks | 3 in, pulled back | Keep a 3-inch gap at the trunk. Mulch volcanoes rot bark and invite borers. |
| Playground and fall zones | 9–12 in | Certified engineered wood fibre only, and check the depth needed for your equipment height. |
How much mulch you actually need
Mulch is sold two ways and the maths is the same for both: area times depth. A 20 by 10 foot bed at 3 inches is 50 cubic feet, which is 1.85 cubic yards, or 25 bags of the standard 2-cubic-foot size.
Two things trip people up. The first is that mulch settles — a freshly spread 3-inch layer is closer to 2.5 inches a fortnight later, which is why this calculator adds a spillage and settling allowance by default. The second is that beds are almost never rectangles. Use the shape buttons and the add-area button to break an irregular bed into pieces rather than guessing a single average.
Bags or bulk?
The crossover is usually around 2 cubic yards, or roughly 27 bags. Below that, delivery fees swamp the per-yard saving. Above it, bulk is normally a third to a half the price of the equivalent bags, and you avoid opening and flattening dozens of plastic sacks.
The catch with bulk is that it arrives as a pile on your driveway and it is your problem until it is moved. One cubic yard is about 14 wheelbarrow loads. If the bed is at the far end of the garden, or you have one afternoon and no help, bags you can carry to the spot may be worth the premium.
Open the price box in the calculator and enter what your yard charges per cubic yard, what a bag costs, and the delivery fee. The ticket will tell you which one wins at your size.
Choosing the material, not just the volume
Shredded hardwood knits together and stays put on slopes. Bark nuggets float and will migrate downhill in heavy rain. Dyed mulches hold colour longer but the dye is the only thing separating a good product from ground-up pallets — check that it is certified free of treated wood.
Coverage is roughly the same across types, so the volume this calculator gives you does not change with material. Weight does: bark nuggets are far lighter than shredded hardwood, which matters if you are hauling it yourself.
Common questions
How many bags of mulch are in a cubic yard?
Thirteen and a half bags of the standard 2-cubic-foot size, or nine bags of the 3-cubic-foot size. A cubic yard is 27 cubic feet, so divide 27 by the bag size printed on the sack.
How much does a cubic yard of mulch cover?
About 108 square feet at 3 inches deep, 162 square feet at 2 inches, or 81 square feet at 4 inches. Coverage and depth trade off directly — halve the depth and you double the area.
How much does a yard of mulch weigh?
Usually 400 to 800 pounds depending on the material and how wet it is. Shredded hardwood soaked by rain sits at the top of that range. It is light enough that volume, not weight, is what limits a pickup load.
Should I remove the old mulch first?
Not usually. Break up any matted crust with a rake and top up to depth. Strip it back only if the total has crept past four inches, or if it has gone sour and smells of vinegar or ammonia.
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