How to use the mulch calculator
- Choose feet and inches or meters and centimeters. Switching units converts the numbers you already typed.
- Pick a shape for each bed and enter its size. Use Add another area for more beds, or switch to Total area if you know the square footage.
- Enter the depth of mulch you want to add.
- Order the cubic yards for a bulk delivery, or the bag count for the bag size your store carries.
Mulch formula
Rectangle: length × width Circle: 3.1416 × (diameter ÷ 2)² Triangle: base × height ÷ 2 Cubic feet = total square feet × (depth in inches ÷ 12) Cubic yards = cubic feet ÷ 27 Cubic meters = cubic yards × 0.7646 Bags = cubic feet ÷ bag size in cubic feet, rounded up
Worked example: a 20 × 6 ft bed at 3 inches
- 20 × 6 = 120 square feet
- 120 × (3 ÷ 12) = 30 cubic feet
- 30 ÷ 27 = 1.11 cubic yards, or 0.85 cubic meters
- Bags: 30 ÷ 2 = 15 bags of 2 cu ft, 20 bags of 1.5 cu ft or 10 bags of 3 cu ft
Add a round tree ring 6 ft across (28.3 sq ft) and a triangle corner bed with an 8 ft base and 5 ft height (20 sq ft), and the total is 168.3 square feet: 42.1 cubic feet, 1.56 cubic yards or 22 bags of 2 cu ft.
How deep should mulch be?
University of Minnesota Extension recommends 2 to 4 inches to balance weed control with air reaching the soil. Clemson Cooperative Extension adds detail by material:
- Fine-textured wood and bark mulch: no more than 2 to 3 inches.
- Coarse pine bark nuggets: up to 4 inches.
- Grass clippings and shredded leaves: no more than 2 inches, because they mat together.
- Keep mulch 2 to 3 inches away from the stems of woody plants.
Mulch coverage table
Square feet covered by one cubic yard and by one bag of each size.
| Depth | 1 cubic yard | 1.5 cu ft bag | 2 cu ft bag | 3 cu ft bag |
|---|---|---|---|---|
| 2 in | 162 sq ft | 9 sq ft | 12 sq ft | 18 sq ft |
| 3 in | 108 sq ft | 6 sq ft | 8 sq ft | 12 sq ft |
| 4 in | 81 sq ft | 4.5 sq ft | 6 sq ft | 9 sq ft |
Bulk or bagged mulch
Bulk mulch is sold and delivered by the cubic yard. Bagged mulch is sold by volume printed on the bag, most often 2 cubic feet. One cubic yard equals 13.5 bags of 2 cu ft, so compare the bag count with the price of a yard plus delivery from a local supplier.
Tips
- Measure the bed itself, not the yard around it, and leave out patios, paths and large shrubs.
- For a curved bed, use the closest rectangle, circle or triangle, or split it into a few of each.
- Topping up an old bed takes less: enter only the depth you are adding.
- Bag counts round up to whole bags, so a small leftover is normal.