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This mulch calculator helps you figure out how much mulch, bark, topsoil or compost you need for garden beds, borders and lawns. Enter the size of the area and the depth you want, and it tells you the volume in cubic yards or cubic meters and how many bags to buy.
How to Use the Mulch and Topsoil Calculator
- Choose the material: mulch or bark, topsoil, or compost.
- Enter the length and width of the bed. For odd shapes, split the area into rectangles and add the results.
- Enter the depth. Mulch is usually spread 2–4 in (5–10 cm) deep.
- Choose the bag size you plan to buy. In the US mulch is often sold in 2 cu ft bags; in the UK and Europe, in 50–75 litre bags.
- Optionally enter the price per bag to see the total cost.
Mulch Formula
Volume = Length × Width × Depth
Number of bags = Volume ÷ Bag size
In the US, convert the depth from inches to feet (divide by 12), multiply to get cubic feet, then divide by 27 for cubic yards. One cubic yard of mulch equals 27 cu ft, or about 13.5 bags of 2 cu ft. In metric, one cubic meter equals 1,000 litres, or 20 bags of 50 litres.
Worked Example: 10 × 10 ft Bed, 3 Inches Deep
- Depth: 3 in ÷ 12 = 0.25 ft
- Volume: 10 × 10 × 0.25 = 25 cu ft = 0.93 cubic yards
- Bags: 25 ÷ 2 = 12.5, so buy 13 bags of 2 cu ft
Metric example: a border 5 m long and 1 m wide covered 7.5 cm deep needs 0.375 m³, or 375 litres, which is 8 bags of 50 litres.
How Deep Should Mulch, Topsoil and Compost Be?
| Material and use | Recommended depth |
|---|---|
| Mulch around shrubs and perennials | 2–3 in (5–7.5 cm) |
| Mulch for weed suppression | 3–4 in (7.5–10 cm) |
| Topsoil for a new lawn | 4–6 in (10–15 cm) |
| Top-dressing an existing lawn | ¼–½ in (0.5–1 cm) |
| Compost worked into beds | 1–3 in (2.5–7.5 cm) |
| Raised vegetable beds | Full bed depth, often 8–12 in (20–30 cm) |
Keep mulch a few inches away from tree trunks and plant stems. Piling it against bark can trap moisture and encourage rot and pests.
Coverage of One Cubic Yard
| Depth | Area covered by 1 cubic yard | Area covered by 1 m³ |
|---|---|---|
| 1 in (2.5 cm) | 324 sq ft | 40 m² |
| 2 in (5 cm) | 162 sq ft | 20 m² |
| 3 in (7.5 cm) | 108 sq ft | 13.3 m² |
| 4 in (10 cm) | 81 sq ft | 10 m² |
Tips for Buying Mulch and Soil
- Bulk mulch is usually cheaper than bags once you need more than about 2–3 cubic yards.
- Topsoil is heavy. A cubic yard can weigh well over a ton, so check whether your vehicle or wheelbarrow can handle it.
- Mulch breaks down and settles, so plan to top it up by an inch or so each year.
- Laying gravel or stone instead of mulch? Try our gravel calculator.
Frequently Asked Questions
How many bags of mulch are in a yard?
One cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cu ft mulch, 18 bags of 1.5 cu ft or 9 bags of 3 cu ft.
How much area does a bag of mulch cover?
A 2 cu ft bag covers about 12 sq ft at 2 inches deep, 8 sq ft at 3 inches deep and 6 sq ft at 4 inches deep.
How much mulch do I need for 100 square feet?
At 3 inches deep, 100 square feet needs 25 cubic feet of mulch, which is about 0.93 cubic yards or 13 bags of 2 cu ft.
How deep should mulch be?
Most beds do well with 2–3 inches (5–7.5 cm) of mulch. Use up to 4 inches for stronger weed control, but avoid piling it against stems and trunks.
Can I use this calculator for topsoil and compost?
Yes. The volume formula is the same. Select topsoil or compost and the calculator also shows an approximate weight for topsoil.
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