Mulch Calculator
To find how much mulch you need, multiply your bed area in square feet by the depth in feet, then divide by 27 for cubic yards — or by 2 for the number of 2 cubic foot bags. This calculator does the math for a topsoil garden bed or landscaping project in any rectangle, circle, or ring shape.
- Volume
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- Weight
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- Bags needed
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How to calculate mulch
- Measure the bed area in square feet — length × width, or π × radius² for a circle.
- Convert the depth to feet by dividing inches by 12 (3 in ÷ 12 = 0.25 ft).
- Multiply area × depth to get the volume in cubic feet.
- Divide the cubic feet by 27 for cubic yards, or by 2 for the number of 2 cubic foot bags.
| Material | Density (lb/ft³) | Tons per cubic yard |
|---|---|---|
| Wood Mulch | 30 | 0.41 |
| Bark | 20 | 0.27 |
| Straw | 12 | 0.16 |
| Depth | Coverage |
|---|---|
| 2 in | 162 sq ft |
| 3 in | 108 sq ft |
| 4 in | 81 sq ft |
Frequently Asked Questions
How many bags of mulch do I need for 100 square feet?
At a standard 3-inch depth, 100 square feet needs 25 cubic feet of mulch, which is about 13 bags of 2 cubic feet each. Deeper mulch beds at 4 inches would need roughly 17 bags for the same area.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so at 2 cubic feet per bag that works out to 27 / 2 = 13.5, rounded up to 14 bags. Buying in bulk by the cubic yard is usually cheaper than buying 14 individual bags.
How deep should mulch be around plants?
Most garden beds do well with 2-3 inches of mulch, which suppresses weeds and retains moisture without smothering roots. Avoid piling mulch against tree trunks or plant stems, and keep it a few inches back to prevent rot.
How much does a cubic yard of mulch weigh?
A cubic yard of wood mulch weighs roughly 400-500 lb, based on a typical density of 20-30 lb/ft³, much lighter than gravel or soil. Straw mulch is lighter still, while denser bark mulch sits toward the higher end of that range.
Should I buy mulch in bags or bulk?
For small beds under about 2 cubic yards, bagged mulch is usually more convenient and not much pricier per cubic foot. Larger projects typically save money buying mulch in bulk by the cubic yard, delivered by truck.
Sources & references
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Last updated: July 2026