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Mulch Calculator
Your garden bed
Example: a 10 × 4 ft bed at 3 inches deep needs 10 cubic feet of mulch, which is 0.37 cubic yards — 5 bags of 2 cubic feet each.
Behind the numbers
How mulch volume works
Mulch is sold by volume: by the cubic yard in bulk, or by the bag in cubic feet. Multiply the bed length by its width to get the area, then multiply by the depth in feet (inches divided by 12). One cubic yard holds 27 cubic feet, so divide cubic feet by 27 for the bulk amount, and divide by the bag size for the number of bags, rounding up.
10 × 4 × (3 ÷ 12) = 40 × 0.25 = 10 cu ft.
10 ÷ 27 = 0.37 cu yd.
10 ÷ 2 = 5 bags of 2 cu ft.
A few comparisons
Worked examples
| Garden bed | Result |
|---|---|
| 10 × 4 ft, 3 in deep | 10 cu ft · 0.37 cu yd · 5 bags |
| 20 × 5 ft, 3 in deep | 25 cu ft · 0.93 cu yd · 13 bags |
| 12 × 8 ft, 2 in deep | 16 cu ft · 0.59 cu yd · 8 bags |
| 6 × 6 ft, 4 in deep | 12 cu ft · 0.44 cu yd · 6 bags |
| 30 × 4 ft, 3 in deep | 30 cu ft · 1.11 cu yd · 15 bags |
| 8 × 3 ft, 2 in deep | 4 cu ft · 0.15 cu yd · 2 bags |
Mulch, without the guesswork.
Spread mulch 2 to 3 inches deep. Thinner layers let weeds through, and deeper than 4 inches can smother roots.
Keep mulch a few inches away from stems and tree trunks. Mulch piled against bark holds moisture and invites rot.
Buy one extra bag beyond the rounded-up count. Beds are rarely perfect rectangles, and a spare bag covers the corners.
For beds bigger than about 10 by 10 feet, bulk mulch by the cubic yard is usually cheaper than the same amount in bags.
Good to know
Your mulch questions, answered.
How much mulch do I need for a 10x4 foot bed?
A 10 by 4 foot bed at 3 inches deep needs 10 cubic feet of mulch, which is 0.37 cubic yards, or 5 bags of 2 cubic feet each.
How deep should mulch be?
Two to 3 inches is right for most garden beds. Less than 2 inches lets weeds through, and more than 4 inches can smother roots and hold too much water.
How many cubic feet are in a cubic yard of mulch?
There are 27 cubic feet in one cubic yard. Divide cubic feet by 27 to get cubic yards, for example 10 cubic feet is 0.37 cubic yards.
Should I buy mulch in bulk or in bags?
Bulk mulch by the cubic yard is usually cheaper for beds larger than about 10 by 10 feet, while bags are easier to carry and store for small beds. One cubic yard fills about thirteen 2-cubic-foot bags.