Bed size and depth in, cubic yards and bag count out. Works for mulch, topsoil, and compost — and tells you when bulk delivery beats hauling bags.
Add up every bed you're covering in this order.
3" is standard for established beds. 4" for bare ground with heavy weed pressure.
Typical US delivered bulk mulch runs $30–$60 per yard, before the delivery fee.
120 sq ft at 3 inches deep
Bags are fine here
Under about 12 bags, bagged mulch fits in a car and costs roughly the same as a bulk minimum.
Volume
Cost comparison
Bulk cost excludes delivery, which is typically $50–$100 and often waived above a few yards.
Mulch is a volume problem: area × depth. The depth is entered in inches and divided by 12 to convert to feet, so a 120 square foot bed at 3 inches is 120 × 0.25 = 30 cubic feet.
Dividing by 27 gives cubic yards, the unit bulk suppliers sell in. Bags are counted by dividing total cubic feet by the bag size and rounding up, since you cannot buy two-thirds of a bag.
No waste factor is applied here, unlike flooring or tile. Mulch is spread rather than cut, so there are no off-cuts — but it does settle, which is why measuring existing depth before a spring top-up matters more than padding the order.
A 30 ft × 4 ft foundation bed at 3 inches deep, 2 cubic foot bags at $4.50, bulk at $45 per yard:
At fifteen bags this is right at the crossover. Bulk is cheaper on material but only wins overall if delivery is free or you can collect it yourself.
Bags win on convenience below roughly 12 to 15. They fit in a car, store dry in a garage, are returnable if unopened, and go straight where they're needed with no wheelbarrow relay. Above that, the price per cubic foot starts to hurt.
Bulk wins clearly above about two cubic yards. A yard of mulch is roughly 12 wheelbarrow loads, so plan for a real afternoon of moving it — and a driveway you can spare while the pile sits there. Most suppliers have a one-yard minimum and charge a delivery fee that is often waived above three or four yards.
A cubic yard is 27 cubic feet, so it takes 13.5 bags at 2 cubic feet each, 9 bags at 3 cubic feet, or 18 bags at 1.5 cubic feet. Two cubic feet is the most common US bag size for shredded hardwood mulch. Once you need more than about 12 to 15 bags, bulk delivery is almost always cheaper per yard even after the delivery fee.
Three inches is the standard for established beds — deep enough to suppress weeds and hold moisture, shallow enough to let water and air reach the roots. Use 2 inches around shallow-rooted plants and in beds you top up every season, and up to 4 inches on new beds or bare ground where weed pressure is high. Deeper than 4 inches starts causing problems rather than solving them.
Yes. Beyond roughly 4 inches, mulch begins to hold excess moisture against roots and can starve them of oxygen. Piling mulch against a tree trunk — the so-called mulch volcano — traps moisture against the bark, invites rot and pests, and encourages roots to grow into the mulch instead of the soil. Always pull mulch back a few inches from trunks and stems.
Organic mulch breaks down and needs topping up annually, usually in spring, though a full replacement is rarely necessary. Measure the existing depth first and add only what brings you back to 3 inches — layering fresh mulch onto an existing 3-inch bed every year is how beds end up 6 inches deep and waterlogged. Rubber and stone mulch do not decompose and are not replaced on a schedule.
Per cubic yard, yes, and usually by a wide margin. Bulk is typically priced at $30 to $60 per yard delivered, while the same volume in 2 cubic foot bags at $4 each works out well above that. The trade-off is that bulk arrives as a pile on your driveway to be moved by wheelbarrow, and you must take the full order, whereas leftover bags can be returned.
Yes — the volume math is identical for any material spread at a uniform depth, including topsoil, compost, and garden soil. Only the coverage advice differs: compost is usually worked in at 1 to 2 inches rather than layered on top, and topsoil for levelling is applied to whatever depth the low spot requires.
Install Calculatory
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