How the mulch calculator works
- Area = length × width, in square feet.
- Volume = area × (depth in inches ÷ 12), in cubic feet.
- Cubic yards = cubic feet ÷ 27, for bulk deliveries.
- Bags = cubic feet ÷ bag size, rounded up.
For a round bed, use the square footage calculator to get the area, then multiply by the depth in feet.
Assumptions
- Beds are rectangular. For curved beds, a rectangle that covers the bed gives a slightly generous estimate.
- The depth is the finished depth after spreading. Fresh, fluffy mulch settles a little over the first few weeks.
- Bag sizes are the volume printed on the bag: most commonly 2 cu ft, sometimes 1.5 or 3 cu ft.
Worked example
A flower bed along the house is 20 ft × 5 ft, mulched 3 in deep.
- Area: 20 × 5 = 100 sq ft
- Volume: 100 × (3 ÷ 12) = 25 cu ft
- Cubic yards: 25 ÷ 27 = 0.93 yd³
- 2 cu ft bags: 25 ÷ 2 = 12.5, which rounds up to 13 bags
Tips before you buy
- Bulk mulch is usually cheaper than bagged once you need more than 2–3 cubic yards.
- Keep mulch a few inches away from tree trunks and house siding to prevent rot and pests.
- Topping up an existing bed? Measure the current depth and only add the difference.
Frequently asked questions
How deep should mulch be?
For most garden beds, 2–3 in is ideal. Going up to 4 in helps suppress weeds in new beds. Thicker than that can stop water and air from reaching the roots.
How many bags of mulch are in a yard?
One cubic yard is 27 cu ft, which is 13.5 bags of 2 cu ft or 9 bags of 3 cu ft.
How much area does a yard of mulch cover?
At 3 in deep, one cubic yard covers about 108 sq ft. At 2 in it covers about 162 sq ft.