Mulch Calculator
Buy this many
42 two-cubic-foot bags
That is 75 cubic feet, or 2.78 cubic yards, before the 10% allowance. A yard is fourteen of these bags, and most garden centres deliver a yard for less than fourteen bags cost.
- 2 cubic foot bags
- 42
- 3 cubic foot bags
- 28
- Or bulk, delivered
- 3 cubic yards
The allowance covers uneven ground, spillage and the last bit that never quite comes out of the barrow. Bagged mulch is also quoted loose, so it beds down thinner than the bag volume suggests — the depth you enter is the settled depth you want to end up with. That allowance is already in the bag counts above; the bulk figure rounds up from the bare volume instead, because a spare cubic yard delivered is a bigger margin than any percentage would add.
How this is calculated
Mulch is priced two completely different ways and the crossover catches people out. Bagged mulch comes in two or three cubic foot bags and is easy to carry, store and spread a bit at a time. Bulk mulch is sold by the cubic yard and delivered in a heap on your driveway. A cubic yard is twenty-seven cubic feet, which you buy as fourteen two-cubic-foot bags, and most garden centres will deliver a yard for less than fourteen bags cost — so the moment a job needs more than about a dozen bags, bulk is usually both cheaper and less driving. The arithmetic itself is area times depth: a bed measured in square feet, a depth in inches, converted to cubic feet and then to cubic yards. Depth is where judgement comes in rather than arithmetic. Two inches suppresses most weeds and is enough for an established bed you top up every year; three is the usual recommendation for a new bed; four starts to hold too much moisture against stems and can do more harm than the weeds would have.
Worked example
Three hundred square feet at three inches is 75 cubic feet, or 2.78 cubic yards. Ten percent on top makes it 82.5 cubic feet to buy, which is 42 of the small bags — two car loads and a lot of plastic — against one delivery. The bulk figure skips that allowance and rounds straight from the raw 2.78 yards up to 3, because a spare cubic yard delivered is already a bigger margin than ten percent would add. At this size the delivery is still almost certainly cheaper, and it is definitely less work.
Inputs: A bed of 300 square feet at 3 inches deep, with a 10% waste allowance
Result: 42 two-cubic-foot bags — 28 three-cubic-foot bags, or 3 cubic yards delivered
What this assumes
- The waste allowance covers uneven ground, spillage and the mulch that never quite comes out of the barrow — the same barrow, over the same ground, as a load of gravel. Bagged mulch is quoted loose, so it beds down thinner than the bag volume suggests, and the depth you enter is the settled depth you want to end up with. Ten percent is a normal starting point.
- Bag sizes are the two common ones. Check yours, because some brands sell 1.5 or 2.8 cubic foot bags and the count changes accordingly.
- Bulk mulch is ordered in whole cubic yards, so that figure rounds up from the raw volume, not from the volume plus the waste allowance above — that allowance is already in the bag counts, and a spare cubic yard delivered is a bigger margin than any percentage would add. Most suppliers have a minimum delivery anyway.
Questions
- How deep should mulch be?
- Two inches on an established bed you top up each year, three on a new one. Four is where it starts working against you — it holds moisture against stems and roots, and piling it up against a trunk is the single most common way a well-mulched tree gets killed.
- Bags or bulk?
- Roughly a dozen bags is the crossover. Below that, bags are easier and the price difference is small. Above it, bulk is usually cheaper per yard, arrives in one delivery instead of several car loads, and leaves you with no plastic to dispose of. The trade is that a heap on the driveway has to be moved before it kills the lawn under it.
- Does mulch really need replacing every year?
- Topping up, not replacing. Organic mulch breaks down into the soil, which is most of the point, so a bed loses perhaps an inch a year. Measure what is left and add the difference rather than laying a fresh three inches over the old, which is how beds end up six inches deep and waterlogged.
- What will the mulch cost?
- Type your price for a two cubic foot bag, or the delivered price per cubic yard, and the result card costs the purchase this page recommends, waste allowance and round-up included. Fill both in and the bags-versus-bulk comparison becomes a number instead of a rule of thumb — bulk usually wins above about two yards, and now you can see by how much. The prices are yours, never ours.