How to use the mulch calculator
- Choose the shape. Rectangle, circle, several parts for L-shapes and curves, or type in the area if you already know it.
- Enter the size and depth. Length and width in feet; depth in inches. Feet and inches like 12' 6" work too.
- Read the result in cubic yards, tons and bags. Under Adjust assumptions you can change the weight per yard, extra and bag size.
- Add your supplier's price per ton, yard or bag to see the cost, including delivery.
The mulch formula
Cubic feet = area (sq ft) × depth (in) ÷ 12
Cubic yards = cubic feet × (1 + extra) ÷ 27
Tons = cubic yards × weight per cubic yard
Bags = cubic feet with extra ÷ bag size, rounded up
Worked example
A 20 × 10 ft bed, 3 inches deep
- Area = 20 × 10 = 200 sq ft.
- Volume = 200 × (3 ÷ 12) = 50 cu ft; with 5% extra = 52.5 cu ft.
- 52.5 ÷ 27 = 1.94 cubic yards, or 52.5 ÷ 2 = 27 bags of 2 cu ft.
How far a cubic yard goes
| Depth | One cubic yard covers | 2 cu ft bags per 10 sq ft |
|---|---|---|
| 1 in | 324 sq ft | 0.4 |
| 2 in | 162 sq ft | 0.8 |
| 3 in | 108 sq ft | 1.2 |
| 4 in | 81 sq ft | 1.7 |
| 6 in | 54 sq ft | 2.5 |
A cubic yard is 27 cubic feet, or 13.5 bags of 2 cu ft.
Mulch types
- Shredded hardwood knits together and stays put on slopes.
- Pine bark nuggets last longer but can float away in heavy rain.
- Pine straw is light and covers more area per bale.
- Rubber mulch does not break down; it is heavier and sold by the bag.
Common mistakes to avoid
- Too deep. More than 4 inches can starve roots of air and water.
- Volcano mulching. Piling mulch against trunks invites rot and pests.
- Forgetting top-ups. Mulch breaks down; most beds need 1 inch added each year, not a full new layer.
- Measuring the whole yard. Measure only the beds, splitting curves into rectangles.
Frequently asked questions
How much mulch do I need?
Multiply the bed area in square feet by the depth in inches, then divide by 324 to get cubic yards. A 200 sq ft bed at 3 inches needs 200 × 3 ÷ 324 = 1.85 cubic yards, about 1.94 with 5% extra.
How deep should mulch be?
2 to 3 inches for most beds, and 3 to 4 inches on paths or where weeds are a problem. Keep mulch a couple of inches away from tree trunks and plant stems.
How many bags of mulch are in a yard?
A cubic yard is 27 cubic feet, so it takes 13.5 bags of 2 cu ft or 9 bags of 3 cu ft.
How much area does a yard of mulch cover?
About 162 sq ft at 2 inches, 108 sq ft at 3 inches and 81 sq ft at 4 inches.
Bags or bulk mulch?
Bags are convenient up to about a yard. Beyond that, bulk delivery is usually far cheaper per yard, though there may be a delivery fee or minimum.
How much does a yard of mulch weigh?
Typically 400 to 800 lb depending on the material and how wet it is. The calculator uses 0.3 tons (600 lb); change it if your supplier gives another figure.