How to use this calculator
Mulch volume is area times depth. Measure the bed the way you will order—then keep depth in inches in the form (the math converts inches to feet).
- Measure bed length and width in feet, or switch to total square feet if you already added irregular shapes as rectangles.
- Enter depth in inches. Two to three inches is common for weed suppression on established beds; the depth field defaults to 3 inches.
- Set waste / settling extra if the bed is uneven or you expect shrinkage after the first rain. The default is 5%.
- Confirm bag size in cubic feet (often 2 cu ft at US big-box stores) if you are buying bags instead of bulk yards.
- Read cubic yards for a bulk order and bags to buy for bagged mulch. Edit price per cubic yard to match your supplier.
How this calculation works
- Area is length × width, or your total square footage for irregular beds added together.
- Depth in inches is converted to feet (divide by 12). Cubic feet = area × depth in feet, then increased by your waste percent.
- Cubic yards = cubic feet ÷ 27. Bags = cubic feet ÷ bag size, rounded up. Bulk cost uses your $/yard on that wasted volume.
cu ft = sq ft × (depth in / 12) × (1+waste%); yards = cu ft / 27; bags = ceil(cu ft / bag size)
Worked example
A straight bed 20 ft long by 8 ft wide, mulched 3 inches deep, with the default 5% waste and 2 cu ft bags—the same starting values as the form.
- Area = 20 × 8 = 160 sq ft.
- Depth in feet = 3 ÷ 12 = 0.25 ft. Net cubic feet = 160 × 0.25 = 40 cu ft.
- With 5% waste: 40 × 1.05 = 42 cu ft.
- Cubic yards = 42 ÷ 27 ≈ 1.56 yd³. Bags = ceil(42 ÷ 2) = 21 bags.
Result: 1.56 cubic yards, 42.0 cubic feet, 21 bags—the same numbers this calculator returns for those inputs.
Common mistakes
- Entering depth as feet in a field that expects inches (for example typing 3 when you meant 3 feet). Depth here is inches; 3 inches is 0.25 feet in the volume math.
- Treating a curved or L-shaped bed as one optimistic rectangle. Break odd shapes into rectangles, add the square feet, and use the area mode.
- Confusing cubic feet with cubic yards. One cubic yard is 27 cubic feet—bulk yards are the smaller number on the ticket.
- Ordering a very shallow or very deep layer without a reason. Many beds use about 2–3 inches of hardwood mulch; deeper can stay wet. Match depth to the plants and the product, not a single fixed rule.
- Assuming every bag is 2 cubic feet. Colored or rubber mulch bags can differ—use the bag label in the bag size field.
What to do next
- Call the supplier for current bulk price; the default is a planning number, not today’s delivery quote.
- Do not pile mulch against siding or tree trunks (volcano mulch). Keep a gap at stems.
- If the bed is full of roots and grade is uneven, add a little extra rather than assuming a perfect rectangle.
Refreshing soil under the mulch? Try the topsoil calculator. For paths or base rock next to the bed, use the gravel calculator. Planning a sitting area beside the planting bed? The patio calculator estimates paver or slab takeoff and an editable installed range.
FAQ
- How much mulch do I need?
- Multiply bed area (sq ft) by depth in feet, convert to cubic yards by dividing by 27, and add any waste percent you choose. This calculator also converts that volume into bags using the bag size you enter. A 20×8 ft bed at 3 inches with 5% waste is about 1.56 cubic yards or 21 bags at 2 cu ft each.
- How many cubic yards of mulch do I need?
- Cubic yards = cubic feet ÷ 27. Cubic feet = square feet × (depth in inches ÷ 12), then × (1 + waste%). Enter your bed size above to see yards for a bulk delivery.
- How deep should mulch be?
- Often 2–3 inches for hardwood mulch on beds. Deeper can stay wet and invite pests. Follow what your plants and climate actually need, not a single internet rule. The depth field on this page defaults to 3 inches and is editable.
- How do I calculate mulch for a garden bed?
- Measure length and width in feet (or total square feet), choose a depth in inches, then convert to cubic feet and yards. For irregular beds, measure as multiple rectangles, add the areas, and use the total-square-feet input mode.
- How many bags of mulch do I need?
- Bags = ceil(cubic feet ÷ bag size). Set bag size to the cubic feet printed on your bag (often 2 cu ft). The calculator rounds up so you do not end one bag short.
- Is a “scoop” the same as a yard?
- No. A loader scoop is whatever that bucket holds. Buy by the cubic yard on a ticket, not by scoops.
Sources
- Volume = area (sq ft) × depth (ft); 1 cubic yard = 27 cubic feet
- Bag count uses the bag size you enter (often 2 cu ft in US big-box stores)
Cost defaults are typical US planning bands, last reviewed 2026-08-25. Edit the price fields on this page rather than treating them as a local market index.