Miscellaneous
Mulch & Soil Calculator - How Much Mulch Do I Need?
Calculate how much mulch or soil you need for garden beds. Enter bed dimensions and desired depth to get cubic feet, cubic yards, and bags to buy.
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How to calculate mulch volume
Multiply the area of each garden bed (length × width) by the desired depth. Because depth is usually given in inches and area in square feet, divide the depth by 12 before multiplying to get cubic feet:
Volume (cu ft) = Length (ft) × Width (ft) × Depth (in) / 12Cubic feet vs. cubic yards
Bagged mulch is typically sold in 2 cu ft bags. Bulk mulch delivered by the truckload is sold by the cubic yard (27 cu ft). This calculator shows both so you can easily compare bagged and bulk pricing.
Recommended depth by material
- Bark mulch / wood chips: 2–3 inches
- Fine compost / topsoil: 1–2 inches as a top-dressing
- Gravel / stone: 2–3 inches
- Straw: 3–4 inches
Tips
- Keep mulch 2–3 inches away from plant stems to prevent rot.
- Add 10–15 % extra when buying to allow for settling and spillage.
- Refresh mulch annually. It decomposes and thins over time.
Mulch types comparison
| Type | Recommended depth | Pros | Cons |
|---|---|---|---|
| Wood chips / bark | 2–3 in | Weed suppression, moisture retention, slow decomposition | Can harbor insects if applied too thick |
| Shredded bark / nuggets | 2–3 in | Attractive, widely available, good insulation | Floats in heavy rain; pine can acidify soil |
| Straw | 3–4 in | Lightweight, great for vegetable gardens | Can introduce weed seeds if not sterile |
| Rubber mulch | 2–3 in | Long-lasting (10+ years), no decomposition | Gets hot in sun, can leach zinc, not organic |
| Gravel / stone | 2–3 in | Permanent, great drainage, low maintenance | Retains heat, heavy, difficult to remove |
Delivery quantities
Bagged mulch is commonly sold in 2 cu ft bags. To find how many bags you need, divide your total cubic feet by 2:
Number of bags = Total volume (cu ft) ÷ 2Bulk mulch from a landscape supplier is sold by the cubic yard (1 cu yd = 27 cu ft). Divide your total cubic feet by 27 to get the number of cubic yards. Bulk is almost always cheaper per cubic foot for large projects (3+ cu yd).
Volcano mulching warning
Volcano mulching - piling mulch against a tree trunk in a cone shape - is one of the most common and damaging landscaping mistakes. Mulch piled against bark traps moisture, promotes fungal disease and rot, and can attract rodents that girdle the bark. Keep mulch 2–3 inches away from the trunk and spread in a flat ring extending to the drip line.