Settings
Bags Needed
Buying Tips
- Under 3 cubic yards: Bags are convenient
- 3+ cubic yards: Bulk delivery is usually cheaper per yard
- 14 bags (2 cu ft) = 1 cubic yard
- 9 bags (3 cu ft) = 1 cubic yard
Ready to buy? Search for mulch:
🌿 How This Mulch Calculator Works
Mulch is sold by volume — cubic yards in bulk, cubic feet in bags — but you measure a garden bed in square feet. Converting between the two is the whole job, and it is one multiplication and one division.
Enter each bed's length and width in feet. The calculator multiplies them for area, multiplies that by the depth you picked (converted from inches to feet), then divides by 27 to get cubic yards — because a cubic yard is 3 ft × 3 ft × 3 ft, or 27 cubic feet. Bag counts come from the same cubic-foot figure divided by the bag size and rounded up to a whole bag.
Formula Reference
Cubic feet = area × (depth ÷ 12)
Cubic yards = cubic feet ÷ 27
Bags = ⌈ (cubic feet ÷ bag size) × (1 + extra ÷ 100) ⌉
Coverage: rearranging the same formula gives the figures garden centres quote. One cubic yard is 27 cubic feet, so at 2 inches (⅙ ft) deep it spreads over 27 ÷ ⅙ = 162 sq ft; at 3 inches, 108 sq ft; at 4 inches, 81 sq ft.
📏 How Deep Should the Mulch Be?
Penn State Extension's Mulching Landscape Trees (David R. Jackson, 2018) is blunt about it: "Apply a 2- to 4-inch layer of organic mulch and no more; use less if the soil is poorly drained." The same publication warns that "more than 4 inches may harm the tree's root system," and that finely textured or double-shredded mulch should go down at only 1 to 2 inches, because those materials allow less oxygen through to the root zone.
That is why the depth selector on this page starts at 1 inch for fine mulch, defaults to 2 inches, and stops at 4. When you are choosing a depth, the texture of the mulch matters more than what is planted in the bed.
🧮 A Worked Example
A front bed 20 ft long and 8 ft wide, mulched 3 inches deep, 2-cubic-foot bags, 10% extra:
- Area: 20 × 8 = 160 sq ft
- Volume: 160 × (3 ÷ 12) = 40 cubic feet
- Cubic yards: 40 ÷ 27 = 1.48
- Bags: (40 ÷ 2) × 1.10 = 22 bags of 2 cu ft, or 15 bags of 3 cu ft
Twenty-two bags is a great deal of lifting for a single bed, which is roughly where bulk delivery starts to look attractive.
📐 What to Enter, and How to Measure It
Length and width are the bed's outer dimensions in feet. A tape along the edge is plenty — a 5% error in a bed measurement usually moves the answer by a bag or two — on the 22-bag example above it moves it by exactly two bag. Curved and kidney-shaped beds are the awkward case: this calculator takes rectangles only, so split an irregular bed into rectangles, add each as its own bed, and accept that you are approximating.
Do not deduct the footprint of shrubs and perennials. Plants displace far less mulch than people expect, and the fiddly strips around them are exactly where a short order shows up.
Extra material covers settling, spillage and the edge you always underestimate. 10% is the default; 15% is the sensible pick for irregular shapes.
⚠️ Common Mistakes
Mulch volcanoes. Penn State calls piling mulch against a trunk "never recommended," warning that it "can cause major tree health problems." Pull mulch 3 to 5 inches back from young trees and 8 to 10 inches from mature ones, and leave the root flare — where the trunk meets the soil — visible.
Topping up without measuring what is already there. Mulch decomposes, but it does not disappear. Rake back last season's layer and measure it before choosing a depth. If two inches are already down, you are topping up an inch, not applying three.
Ordering by area instead of volume. "Enough for 500 square feet" is meaningless without a depth attached — at 2 inches that is 3.1 cubic yards, at 4 inches it is 6.2. Always quote a supplier both numbers.
📦 Bags or Bulk?
Bags win on convenience and on where you can park. One cubic yard is 14 bags of 2 cubic feet or 9 bags of 3 cubic feet, so anything past two or three cubic yards means a lot of plastic and a lot of trips. Bulk is priced by the cubic yard and normally works out cheaper at that scale, but you need somewhere to drop the pile and a day to move it. Delivered prices vary too much by region and material for us to print a figure worth trusting — ring two local yards with your cubic-yard number.
❓ Questions People Actually Ask
Is 2 inches of mulch enough?
For most landscape beds, yes. Penn State Extension recommends a 2- to 4-inch layer of organic mulch and no more, and less where soil is poorly drained. Finely textured or double-shredded mulch should be held to 1 to 2 inches. Two inches is this calculator's default for that reason.
What is the 3-3-3 mulch rule?
A memory aid for mulching around a tree. The Arbor Day Foundation states it as keeping mulch "3 inches from the trunk, 3 inches deep, and about 3 feet in diameter around the tree." It is shorthand, not a standard, and it does not fully agree with extension guidance — Penn State puts the trunk gap at 3 to 5 inches for young trees and 8 to 10 inches for mature ones, and caps finely textured mulch at 1 to 2 inches deep rather than 3.
How much will 25 bags of mulch cover?
Twenty-five 2-cubic-foot bags hold 50 cubic feet: 300 sq ft at 2 inches deep, or 200 sq ft at 3 inches. Twenty-five 3-cubic-foot bags hold 75 cubic feet — 450 sq ft at 2 inches, 300 sq ft at 3 inches. A bag count tells you nothing until a depth is fixed.
What does 7 cubic yards of mulch look like?
189 cubic feet. Spread 2 inches deep it covers 1,134 sq ft; at 3 inches, 756 sq ft — roughly a 27-foot square. As a delivered pile it is more material than most driveways comfortably take, which is usually the real constraint.
This is a materials estimate for ordering. It assumes flat, rectangular beds at a uniform depth, and it accounts for neither slope, nor mulch already on the ground, nor settling after the first heavy rain. It does not tell you which mulch suits your planting, and it is not a substitute for advice from an arborist where trees are involved.
Mulch depth guidance on this page comes from Penn State Extension's Mulching Landscape Trees (David R. Jackson, 2018), which is the source for the 2–4 inch range, the 1–2 inch limit on finely textured mulch, the trunk clearances, and the warning against volcano mulching. The 3-3-3 rule is quoted from the Arbor Day Foundation. The four FAQ questions were captured verbatim from Google's People Also Ask panel for "how much mulch do I need" on 31 July 2026. Deeper background on mulch types and bed preparation is in our landscaping guide.