How Much Mulch Do I Need? Bags vs Cubic Yards (With Coverage Chart)
One cubic yard of mulch covers about 108 ft² at 3 in deep, which is the same as 13.5 bags of 2 ft³. Here is the full coverage chart, the recommended depth and how to measure awkward beds.
How deep should mulch be?
Depth decides everything else, so start there. The University of Maryland Extension recommends keeping mulch shallow. It gives 1–3 in for bark mulch and wood chips, and says to keep mulch about 3 in away from tree trunks so it never touches the bark. Its guide also shows a mulch “volcano” piled against a trunk as an example of what not to do. If a bed already has old mulch, measure what’s left and top it up to the target depth rather than adding a full new layer.
Coverage chart
| Depth | 1 cubic yard covers | One 2 ft³ bag covers | One 3 ft³ bag covers |
|---|---|---|---|
| 1 in | 324 ft² | 24 ft² | 36 ft² |
| 2 in | 162 ft² | 12 ft² | 18 ft² |
| 3 in | 108 ft² | 8 ft² | 12 ft² |
| Depth | 1 m³ covers | One 50 L bag covers | One 70 L bag covers |
|---|---|---|---|
| 25 mm | 40 m² | 2.0 m² | 2.8 m² |
| 50 mm | 20 m² | 1.0 m² | 1.4 m² |
| 75 mm | 13.3 m² | 0.67 m² | 0.93 m² |
The math behind it: coverage = volume ÷ depth. A cubic yard is 27 ft³, and 1 in is 1/12 ft, so 27 ÷ (1/12) = 324 ft² at 1 in. Bags work the same way: a 2 ft³ bag at 2 in (1/6 ft) covers 2 × 6 = 12 ft².
Bags or bulk?
A cubic yard equals 13.5 bags of 2 ft³ or 9 bags of 3 ft³. In practice:
- Bags are easy to carry, store and spread a bit at a time. They suit small beds, top-ups and places without vehicle access.
- Bulk (by the cubic yard or m³) is usually cheaper per unit once you need a yard or more, but check the delivery fee and minimum load. You also need somewhere to tip it.
The quickest way to compare is to divide the bulk price plus delivery by the number of yards, and compare that with 13.5 × the price of one 2 ft³ bag.
Measuring beds that aren’t rectangles
- Rectangles: length × width.
- Tree rings: π × radius². A ring 6 ft across (3 ft radius) is about 28 ft². Subtract the trunk if it’s large.
- Curvy borders: measure the length along the middle of the bed and the average width (take three or four widths and average them), then multiply.
- Irregular beds: split them into rectangles, triangles (½ × base × height) and circles, then add them up. Our square footage guide shows how.
Worked examples
Two border beds
Two beds of 20 × 4 ft make 160 ft². Topping up to 3 in: 160 × 3 ÷ 324 = 1.48 cubic yards, or 40 ft³, which is 20 bags of 2 ft³. If last year’s mulch is still 1 in deep, you only need to add 2 in: 0.99 yards or 14 bags.
Three tree rings
Three rings each 6 ft across: 3 × 28.3 = 85 ft². At 3 in deep: 85 × 3 ÷ 324 = 0.79 cubic yards, or about 11 bags of 2 ft³. Leave a mulch-free gap of about 3 in around each trunk.
A UK front garden (metric)
Beds totalling 12 m² at 50 mm: 12 × 0.05 = 0.6 m³ = 600 L, so 12 bags of 50 L.
Tips
- Weed and water the bed before mulching. Mulch helps keep moisture in and weeds down, but it doesn’t kill established weeds.
- Don’t pile mulch against stems, trunks or house siding.
- Bagged mulch volume is printed on the bag; use that number, not the bag’s weight.
The mulch calculator handles rectangles, circles and known areas, in imperial or metric.
Frequently asked questions
How many bags of mulch are in a yard?
13.5 bags of 2 ft³, or 9 bags of 3 ft³. A cubic yard is 27 ft³.
How much area does a yard of mulch cover?
About 324 ft² at 1 in, 162 ft² at 2 in and 108 ft² at 3 in.
How deep should I mulch?
The University of Maryland Extension recommends 1–3 in for bark mulch and wood chips, kept about 3 in away from tree trunks.
How many 2 cu ft bags of mulch do I need for 100 square feet?
At 2 in deep, about 9 bags (100 ÷ 12 = 8.3, rounded up). At 3 in deep, about 13 bags.