How to use the mulch calculator
- Measure each bed's length and width in feet. For several beds or odd shapes, work out each area separately, add them up, and type the total into the area box instead.
- Choose a depth. Two to three inches is a common recommendation for suppressing weeds and holding moisture. Topping up an existing layer may only need one inch.
- Press Calculate to see cubic yards (how bulk mulch is sold) and the number of bags at the two most common bag sizes.
Buying tips: bulk mulch is usually sold by the cubic yard and delivered by truck, while bagged mulch is sold in 2 or 3 cubic foot bags. It helps to know both figures before comparing prices. If you're refreshing an existing bed, measure the depth of what is already there with a ruler, then calculate only the extra depth you need to add.
How it's calculated
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size, rounded up
Depth is divided by 12 to turn inches into feet, and one cubic yard is 3 ft × 3 ft × 3 ft = 27 cubic feet. Bag counts are always rounded up so you don't come up short. For circular beds, the area is π × radius², so a bed 8 ft across has an area of about 3.1416 × 4² ≈ 50.3 sq ft.
Mulch settles over the first few weeks, so some gardeners add about 10% to the result.
Worked example
A 20 × 10 ft front bed at 3 inches deep:
- Area: 20 × 10 = 200 sq ft
- Volume: 200 × 3 ÷ 12 = 50 cu ft
- Cubic yards: 50 ÷ 27 = 1.85 yd³
- Bags: 25 bags of 2 cu ft, or 17 bags of 3 cu ft (16.7 rounded up)
A larger 500 sq ft planting area at 2 inches needs 500 × 2 ÷ 12 = 83.3 cu ft, which is 3.09 cubic yards, 42 two-cubic-foot bags or 28 three-cubic-foot bags.
FAQ
How much area does a cubic yard of mulch cover?
One cubic yard covers about 108 sq ft at 3 inches deep, 162 sq ft at 2 inches, or 324 sq ft at 1 inch.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it equals 13.5 two-cubic-foot bags or 9 three-cubic-foot bags.
How deep should mulch be?
Two to three inches is a common guideline for garden beds. Keep mulch a few inches away from tree trunks and plant stems to avoid rot.
Is bulk mulch cheaper than bags?
Often, for larger jobs, but delivery fees vary. Compare the delivered bulk price per cubic yard with the bag price × 13.5 (2 cu ft bags) or × 9 (3 cu ft bags).