Mulch Calculator
Find how much mulch you need for your garden beds, and how many bags to buy. Enter each bed's shape, size, and depth. A layer 2 to 3 in (5 to 7.5 cm) deep suits most beds. For gravel or stone, use the Gravel Calculator. For topsoil or garden soil to fill a bed, use the Soil Calculator.
Add more beds, or subtract areas that need no mulch, such as a path.
- Choose US or Metric. This also sets the bag sizes in the results: 3, 2, and 1.5 cu ft bags for US, and 100 to 50 L bags for Metric.
- Pick the shape of the bed and enter its dimensions and Depth. A depth of 2 to 3 in (5 to 7.5 cm) is a common choice. For a shape that is not listed, choose Known area and enter the area directly.
- Use Add section for each extra bed. Set a section to Subtract for parts that do not need mulch, such as a path or stepping stones inside a bed.
- Keep the 10% waste allowance or change it. If you change it, Reset to 10% brings it back.
- If your bag size is not listed, enter the volume printed on the bag in Custom bag size to add it to the results.
- Optionally, enter a price per bag, per custom bag, or per cubic yard, cubic foot, or cubic meter to estimate the cost.
For a ring of mulch around a tree, choose Ring. Enter the width of the mulched circle as Outer diameter and the width of the trunk as Inner diameter.
The dimension and depth fields accept whole numbers, decimals, fractions,
and mixed numbers, such as 12, 10.5,
3/4, or 2 1/2. Choose ft + in
as the unit to enter a length such as 12 ft 6 in in two fields.
How much mulch you need
The volume of a layer of mulch of even depth is:
Volume = area × depth
Convert every dimension to the same unit before you multiply. With dimensions in feet, divide cubic feet by 27 to get cubic yards. The waste allowance is added after subtracting any sections: total = net volume × (1 + waste % ÷ 100).
The number of bags is:
Bags = total volume ÷ volume per bag, rounded up
Mulch is sold by volume, and the volume on the bag is the loose volume you spread. The calculator shows these common bag sizes:
| Bag | Examples |
|---|---|
| 3 ft³ | Cypress and pine bark mulch (Cowart, Cypress Elite) |
| 2 ft³ | Scotts Nature Scapes, Vigoro, Timberline |
| 1.5 ft³ | Scotts Nature Scapes, Earthgro |
| 100 L | Westland Landscape Bark (UK) |
| 70 L | Westland Composted Bark (UK), Richgro Pinebark Mulch (Australia) |
| 60 L | Melcourt Ornamental Bark Mulch (UK) |
| 56.6 L | Vigoro 2 cu ft bag, labeled 56.6 L (Canada) |
| 50 L | Supagrow Bark Chippings (UK), Pinegro Pine Bark Mulch (Australia) |
In Canada, 2 cu ft bags are labeled 56.6 L, so the calculator uses 56.6 L to match the label. The 10% waste allowance covers the settling of fresh mulch: the UK mulch maker Melcourt recommends allowing 5 to 10% for natural settlement, and the calculator uses the upper end so you are less likely to run short.
How deep should mulch be?
The Royal Horticultural Society recommends a layer at least 5 cm (2 in) thick, and ideally 7.5 cm (3 in). The right depth also depends on the plants, the soil, and the mulch:
- Iowa State University suggests 3 to 4 in around trees and shrubs on well-drained soil, and 2 to 3 in on heavy soil.
- Mulch makers give their own guidance, such as 3 in for Scotts Nature Scapes, or 50 to 100 mm for Melcourt's bark mulch.
Follow the label on the mulch you buy, or local advice for your plants, and enter that depth in the calculator.
Examples
A square bed
A 10 ft × 10 ft bed, 3 in deep, is 25 ft³. With a 10% waste allowance, the total is 27.5 ft³, or 1.02 yd³ (0.78 m³). That is 10 bags of 3 cu ft, 14 bags of 2 cu ft (27.5 ÷ 2 = 13.75, rounded up), or 19 bags of 1.5 cu ft. At $4.50 per 2 cu ft bag, the cost is $63.00.
Metric dimensions
A 4 m × 2.5 m bed, 7.5 cm deep, is 0.75 m³. With 10% added, the total is 825 L, shown as 0.83 m³. That is 9 bags of 100 L (825 ÷ 100 = 8.25, rounded up), 12 bags of 70 L, or 17 bags of 50 L.
FAQ
A cubic yard is 27 ft³, so it takes 13.5 bags of 2 cu ft (buy 14), 9 bags of 3 cu ft, or 18 bags of 1.5 cu ft.
About 162 ft² at 2 in deep, and 108 ft² at 3 in deep. Divide 27 ft³ by the depth in feet: 27 ÷ (3 ÷ 12) = 108.
It depends on the size of the job and the prices near you. To compare, enter the bag price to see the cost in bags, then switch the price to per cubic yard or cubic meter and enter a bulk quote.
About 1.02 yd³ (27.5 ft³) for a 10 ft × 10 ft bed 3 in deep, with a 10% waste allowance. That's 14 bags of 2 cu ft or 10 bags of 3 cu ft. For a different depth, enter it in the calculator.
Related calculators
- Cubic Yard Calculator
Volume in cubic yards from length, width, and depth.
- Gravel Calculator
Gravel volume and weight in tons, and how many bags to buy.
- Soil Calculator
Soil volume for raised beds and pots, and how many bags to buy.
- Plant Spacing Calculator
How many plants you need for a garden bed from the plant spacing, in a grid or triangular layout.
- Asphalt Calculator
Tons of asphalt for a driveway or parking area from its size and compacted thickness.
- Paver Calculator
How many pavers to buy for a patio or driveway, with the bedding sand and base.