About this calculator
Mulch is sold two ways: in bags measured in cubic feet, or in bulk by the cubic yard. This calculator converts your bed’s dimensions and the depth you want into both, and compares the cost so you can see when a bulk delivery pays off.
It works for shredded bark, wood chips, pine straw sold by volume, rubber mulch and compost top-dressing.
How to use it
- Measure the length and width of the bed. For curved or irregular beds, split them into rectangles and add the results, or measure the average width.
- Choose a depth: 2–3 in refreshes an existing bed, 3–4 in for new beds or weed suppression.
- Pick the bag size sold at your store — most are 2 cu ft, some 3 cu ft.
- Enter local bag and bulk prices to compare costs.
The formula
Volume (cu ft) = length (ft) × width (ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size, rounded up
One cubic yard covers about 108 sq ft at 3 in deep, 162 sq ft at 2 in, or 324 sq ft at 1 in. It takes 13.5 two-cubic-foot bags to make one cubic yard.
Worked example
These are the calculator’s starting values and the results they produce:
| Bed length | 20 ft |
|---|---|
| Bed width | 10 ft |
| Mulch depth | 3 in |
| Bag size | 2 cu ft bag |
| Price per bag | $4.00 |
| Bulk price per cubic yard | $40.00 |
Tips before you buy
- Keep mulch 2–3 in away from tree trunks and plant stems to prevent rot — avoid “mulch volcanoes”.
- Bulk mulch is usually far cheaper per yard than bags once you need more than 2–3 cubic yards, even after delivery fees.
- If you’re topping up an existing bed, measure how much is already there and only add the difference.
- Lay landscape fabric or cardboard underneath in new beds for extra weed control.
Frequently asked questions
How many bags of mulch are in a yard?
13.5 bags of 2 cu ft mulch, or 9 bags of 3 cu ft mulch, make one cubic yard (27 cubic feet).
How much area does a yard of mulch cover?
One cubic yard covers about 324 sq ft at 1 in deep, 162 sq ft at 2 in, 108 sq ft at 3 in and 81 sq ft at 4 in.
How deep should mulch be?
2–3 in is right for most garden beds. Go to 3–4 in for weed suppression in new beds, but no deeper — thick mulch can starve roots of oxygen.
How many bags of mulch do I need for a 10×20 bed?
A 10 × 20 ft bed at 3 in deep needs 50 cubic feet — 1.85 cubic yards, or 25 bags of 2 cu ft mulch.