Enter the size of your beds and how deep you want the mulch to see how many cubic yards or bags to buy, and whether bulk or bagged mulch costs less.
How to use the mulch calculator
- Measure each bed. Enter a rectangle, or pick a circle for the ring around a tree.
- Enter the depth to add. If old mulch is still there, enter only the depth you’re adding on top.
- Choose your bag size, then enter the price per bag or per cubic yard to see the cost.
- For several beds, run each one and add the results, or add their areas first with the square footage calculator.
Mulch formulas
Cubic feet = length (ft) × width (ft) × depth (in) ÷ 12 Cubic yards = cubic feet ÷ 27 Bags = cubic feet ÷ bag size (ft³), rounded up Coverage of 1 yd³ (ft²) = 324 ÷ depth (in)
How deep should mulch be?
University of Illinois Extension recommends mulch 2 to 3 inches deep and warns against “mulch volcanoes”, mulch piled up against a
tree trunk, which can cause bark rot and other damage. Keep mulch pulled back from trunks and stems.
Worked example: a 3 × 40 ft border, 3 in deep
- Area: 3 × 40 = 120 ft².
- Volume: 120 × 3 ÷ 12 = 30 ft³.
- Cubic yards: 30 ÷ 27 = 1.11 yd³.
- Bags: 30 ÷ 2 = 15 bags of 2 cu ft.
A 6 ft ring around a tree at 3 in deep takes 7.1 ft³, or 4 bags of 2 cu ft. Topping up the same border with
1 in of fresh mulch takes 10 ft³, just 5 bags.
Coverage by depth
| Depth | Per cubic yard | Per 2 cu ft bag | Per 3 cu ft bag |
|---|---|---|---|
| 1 in | 324 ft² | 24 ft² | 36 ft² |
| 2 in | 162 ft² | 12 ft² | 18 ft² |
| 3 in | 108 ft² | 8 ft² | 12 ft² |
| 4 in | 81 ft² | 6 ft² | 9 ft² |
Bags or bulk?
A cubic yard is 13.5 bags of 2 cu ft, 9 bags of 3 cu ft or 18 bags of 1.5 cu ft. Multiply your
bag price by that number and compare it with the bulk price per yard plus delivery. Enter either price above and the calculator does
the math for your beds.
Tips
- Weed and water first. Mulch holds moisture in; start with damp soil and a clean bed.
- Keep it off the house. Leave a gap between mulch and siding.
- Don’t pile on every year. Check the depth first; old mulch breaks down but doesn’t always disappear.
- Planting too? The topsoil calculator estimates soil for new beds.
Questions
How many bags of mulch are in a yard?
13.5 bags of 2 cu ft, 9 bags of 3 cu ft or 18 bags of 1.5 cu ft.
How much area does a yard of mulch cover?
162 ft² at 2 in deep, 108 ft² at 3 in and 81 ft² at 4 in.
How much does a yard of mulch weigh?
About 500–800 lb, or roughly a third of a ton, per North Bay Materials. Wet mulch is heavier.
How deep should I lay mulch?
2 to 3 in, per University of Illinois Extension, and never mounded against trunks.
Sources
- Too much of a good thing: mulch volcanoes slowly kill trees, University of Illinois Extension, Aug 26, 2020.
Used for: Mulch 2 to 3 inches deep; avoid mounding against trunks. - Landscape Materials Density Chart, North Bay Materials.
Used for: Typical weights per cubic yard for gravel, sand, dirt and mulch.