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- Mulch needed in cubic feet = bed area × depth in inches ÷ 12.
- Divide cubic feet by 27 for cubic yards, or by the bag size for bags.
- A 20 ft × 5 ft bed at 3 inches deep needs 0.93 cubic yards, or 13 bags of 2 cubic feet.
- One cubic yard covers 108 square feet at 3 inches deep.
How to use the mulch calculator
Choose the bed shape
Pick rectangle or circle, or enter the area if you already know it.
Enter the size
Type the length and width, or the diameter, in feet.
Set the depth
Enter the mulch depth in inches. 2 to 3 inches is typical.
Read the result
You get cubic yards and cubic feet, the number of bags, and how far a cubic yard covers at your depth. Add a bag price for the cost.
How to calculate how much mulch you need
Mulch is sold in bags (by the cubic foot) and in bulk (by the cubic yard). Find the area of the bed, multiply by the depth, and convert the volume to the unit you will buy.
Mulch volume
Cubic feet = area (sq ft) × depth (in) ÷ 12
Cubic yards = cubic feet ÷ 27
Bags = cubic feet ÷ bag size, rounded up
Coverage of one cubic yard = 324 ÷ depth in inches (sq ft)
One cubic yard holds 27 cubic feet, so it equals 13.5 bags of 2 cubic feet.
Worked examples
A 20 ft × 5 ft garden bed, 3 inches deep
100 sq ft × 3 ÷ 12 = 25 cubic feet.
You would round up to 13 bags.
A round bed 8 ft across
Area = π × 4² = 50.27 sq ft at 3 inches deep.
Use the circle option for tree rings and round beds.
Mulch coverage chart
What one cubic yard covers
By depth.
Deeper layers cover less ground.
Where a mulch calculator helps
Garden beds
Find the right amount for flower and shrub beds.
Around trees
Calculate a ring of mulch with the circle option.
Bags or bulk
Compare the cost of bags with a bulk delivery.
Large areas
Measure big beds with the square footage calculator.
A depth of 2 to 3 inches is commonly advised for most beds. Keep mulch pulled back from tree trunks and plant stems rather than piling it against them. Mulch settles and breaks down over time, so you may need to top it up. Needs differ by plant and climate, so check advice for your garden.
Mulch calculator FAQ
How do I calculate how much mulch I need?
Multiply the bed area by the depth in inches, divide by 12 to get cubic feet, then divide by 27 for cubic yards or by the bag size for bags.
How many bags of mulch are in a cubic yard?
A cubic yard is 27 cubic feet, so it equals 13.5 bags of 2 cubic feet, or 18 bags of 1.5 cubic feet.
How deep should mulch be?
2 to 3 inches is commonly advised for garden beds. Use less for fine mulch and keep it off plant stems.
How much area does a yard of mulch cover?
About 108 square feet at 3 inches deep, 162 at 2 inches and 324 at 1 inch.
Is bulk mulch cheaper than bags?
Often yes once you need more than a couple of cubic yards, but delivery fees and minimum loads vary, so compare local prices.
Should I add extra?
Add 5% to 10% for uneven ground or settling, using the extra field in the advanced options.