Mulch Calculator
Enter the size of your garden bed and how deep you want the mulch to see how many cubic yards and bags to buy. You can add a price per bag to estimate the cost.
How to use this mulch calculator
- Measure the length and width of the bed. For an odd shape, break it into rectangles and calculate each one, or estimate its area with the Square Footage Calculator.
- Enter the mulch depth you plan to spread and choose inches or centimeters.
- Keep or change the extra percentage. Use 0 if you want the exact volume.
- Enter the bag size from the label. Add the price per bag if you want a cost estimate.
- Press Calculate, then use Copy result or Export CSV to keep the numbers for your shopping trip.
How to calculate how much mulch you need
Mulch is a layer of material over a flat area, so its volume is the area multiplied by the depth. The calculator then shows that volume in cubic yards and in bags.
- Cubic feet = length (ft) x width (ft) x depth (in) / 12 x (1 + extra % / 100)
- Cubic yards = cubic feet / 27
- Bags = cubic feet / bag size, rounded up to a whole bag
- Cost = bags x price per bag
As a quick check, one cubic yard covers about 108 square feet at 3 inches deep, because 27 cubic feet / 0.25 ft = 108 sq ft.
Worked example
A flower bed measures 15 ft by 6 ft and you want mulch 3 inches deep. Depth in feet = 3 / 12 = 0.25 ft. Volume = 15 x 6 x 0.25 = 22.5 cubic feet. With 5% extra: 23.6 cubic feet, which is 0.88 cubic yards. With 2 cubic foot bags: 23.6 / 2 = 11.8, so you need 12 bags. At $4.50 per bag the estimate is 12 x 4.50 = $54.00.
If you would rather have bulk delivery, 0.88 cubic yards would usually be ordered as 1 cubic yard.
Assumptions & limits
- The bed is flat and the mulch depth is even. Mounded or sloped beds need more material.
- The default bag size of 2 cubic feet is an editable placeholder. Bag sizes vary, so use the figure on the label.
- The price is your own input. The calculator does not look up prices.
- The right depth depends on the mulch type, the plants and local advice. The calculator does not recommend a depth.
- Bagged and bulk mulch can settle or compact, so your result is an estimate.
Frequently asked questions
How do I calculate how much mulch I need?
Multiply length by width in feet, multiply by the depth in feet (inches divided by 12), then divide by 27 for cubic yards. A 10 ft by 10 ft bed at 3 inches deep is 25 cubic feet, or 0.93 cubic yards.
How many square feet does a cubic yard of mulch cover?
About 108 square feet at 3 inches deep, 162 square feet at 2 inches deep and 324 square feet at 1 inch deep. These follow from 27 cubic feet divided by the depth in feet.
How many bags of mulch are in a cubic yard?
Divide 27 by the bag size in cubic feet. With 2 cubic foot bags, a cubic yard is 13.5 bags, so you would buy 14 bags.
How deep should mulch be?
It depends on the mulch, the plants and your climate, so follow local gardening advice. The calculator uses whatever depth you enter.
Is it cheaper to buy mulch in bulk?
Often bulk is cheaper per cubic foot for larger areas, but delivery fees and minimum orders apply. Compare your local prices using the cost estimate.
Should I add extra to the order?
A small allowance covers uneven ground and settling. The calculator starts at 5 percent and you can change it.
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Last updated: November 2026