Mulch Calculator
Enter the area of your bed and how deep you want the mulch — get the volume and the number of bags to buy.
Three answers at once
The result shows cubic yards for bulk orders, cubic feet for the raw volume, and the number of standard 2-cubic-foot bags.
US units
Area is in square feet, depth in inches, and bags are the 2-cubic-foot size sold at most garden centers.
How much mulch do I need?
Volume from area and depth
Mulch is sold by volume, so the amount you need depends on two things: the area you want to cover and how deep the layer should be. This calculator turns those two numbers into a volume — in cubic yards and cubic feet — and into the count of standard 2-cubic-foot bags, so you can order bulk or buy bags with confidence.
Mulch depth is given in inches but area in square feet, so the depth is first divided by 12 to convert it to feet. Multiplying by the area gives the volume in cubic feet, which is then divided by 27 for cubic yards and by 2 for the number of bags.
Cubic feet = area × (depth ÷ 12); cubic yards = cubic feet ÷ 27Because mulch is sold in whole bags, the bag count is always rounded up — 25 cubic feet divided by 2 is 12.5, which rounds to 13 bags so you never come up short.
Suppose you have a 100-square-foot bed and want a 3-inch mulch layer.
Convert depth to feet
3 inches ÷ 12 = 0.25 ft.Multiply by the area
100 sq ft × 0.25 ft = 25 cubic feet.Convert to cubic yards
25 ÷ 27 = 0.93 cubic yards.Count the bags
25 ÷ 2 = 12.5, rounded up to 13 bags.
A depth of 2–3 inches suits most garden beds — enough to suppress weeds and hold moisture without smothering roots. As a rule of thumb, one cubic yard of mulch covers about 100 square feet at a 3-inch depth, which is why bulk mulch is usually ordered by the yard. Each standard bag holds 2 cubic feet, so 13 to 14 bags make up roughly one cubic yard. If your bed is much larger than a few hundred square feet, bulk delivery by the cubic yard is almost always cheaper than buying bags.
The arithmetic is exact, but real-world mulch behaves a little differently.
Settling and bag sizes vary
Loose mulch settles and compresses after spreading and watering, so buying a little extra is wise — many gardeners add about 10%. Bag volumes also vary by brand and material: shredded bark bags are commonly 2 cubic feet, but some are sold at 1.5 or 3 cubic feet. Check the bag before relying on the count, and treat the result as a close estimate rather than an exact order.