Mulch Calculator
Work out how much mulch you need for garden beds and borders. Enter the area and depth to get the volume in cubic yards and the number of standard 2 ft³ bags, with a waste allowance.
Mulch needed
13.5 standard bags make 1 cubic yard. Over ~1 yard, bulk is usually cheaper.
How to calculate mulch
Mulch is estimated from the bed area and the depth you want to spread it. Find the area in square feet (length times width, or π times radius squared for a round bed), multiply by the depth in feet (depth in inches ÷ 12) to get cubic feet, then divide by 27 for cubic yards. Because mulch is most often sold in standard 2 cubic foot bags, the calculator also divides the volume by 2 and rounds up to give you a bag count. The formula is cubic feet = area (ft²) × depth (in) ÷ 12.
There are 27 cubic feet in a cubic yard, so a cubic yard is 13.5 standard bags. That number is the quick way to decide between bags and bulk: if your project needs more than about 14 bags, a bulk cubic-yard delivery is usually cheaper and saves hauling bags from the car.
How deep should mulch be?
For most garden beds, 2 to 3 inches is the sweet spot. That is deep enough to block light and suppress weeds and to slow evaporation so the soil stays moist, but not so deep that it smothers roots or holds water against stems. Keep mulch pulled back a couple of inches from plant stems and tree trunks to avoid rot and pests. If you are refreshing an existing bed that already has some mulch, measure only the additional depth you need to top it up.
A worked example
For a 20 ft by 5 ft border at 3 inches deep, the area is 100 square feet and the volume is 100 × (3 ÷ 12) = 25 cubic feet, which is about 0.93 cubic yards or roughly 13 standard bags. Adding a small waste allowance for uneven spreading nudges that to 14 bags, right at the point where a bulk yard becomes worth considering.
Bags, bulk and waste
Bagged mulch is clean, easy to carry and good for small or awkward beds. Bulk delivery wins on price once you are past about a cubic yard. Either way, add about 5 percent for settling and uneven coverage. If your landscaping project also needs soil under the planting or a gravel path alongside, size them with the topsoil calculator and the gravel calculator. Every tool here runs in your browser and keeps your measurements on your own device.