How much mulch do I need?
Multiply square feet by the depth in inches and divide by 324 to get cubic yards.
cubic yards of mulch = square feet × depth in inches ÷ 324
One cubic yard spread 1 inch deep covers 324 square feet, so divide by 324 and multiply by the depth.[1] The default bed above, 24 × 6 ft at 3 inches, is 144 × 3 ÷ 324 = 1.33 cubic yards, or 36 cubic feet. In 2 cu ft bags that is 18 bags.
Iowa State's worked example rounds a result of 16.56 bags up to 17,[3] and the calculator does the same: bag counts are always rounded up.
Mulch calculator: yards by square feet and depth
100 sq ft of mulch 3 inches deep is 0.93 cubic yards, or 13 bags of 2 cu ft.
| Area | 2 in | 3 in | 4 in |
|---|---|---|---|
| 25 sq ft | 0.15 yd³ (3 bags) | 0.23 yd³ (4 bags) | 0.31 yd³ (5 bags) |
| 50 sq ft | 0.31 yd³ (5 bags) | 0.46 yd³ (7 bags) | 0.62 yd³ (9 bags) |
| 100 sq ft | 0.62 yd³ (9 bags) | 0.93 yd³ (13 bags) | 1.23 yd³ (17 bags) |
| 200 sq ft | 1.23 yd³ (17 bags) | 1.85 yd³ (25 bags) | 2.47 yd³ (34 bags) |
| 500 sq ft | 3.09 yd³ (42 bags) | 4.63 yd³ (63 bags) | 6.17 yd³ (84 bags) |
| 1,000 sq ft | 6.17 yd³ (84 bags) | 9.26 yd³ (125 bags) | 12.35 yd³ (167 bags) |
How deep to spread mulch
Spread mulch 2–4 inches deep: 2–3 inches for fine mulch and up to 4 inches for coarse bark.
Recommended depths depend on the texture of the mulch. Coarse material can go deeper because air and water still move through it; fine material packs down and should stay thinner.
| Mulch | Depth | Source |
|---|---|---|
| Shredded or chipped hardwood | 2–4 in | [3] |
| Fine wood or bark mulch | no more than 2–3 in | [1] |
| Composted material | 2–3 in | [2] |
| Coarse mulch, pine-bark nuggets | 3–4 in | [2][1] |
| Grass clippings, shredded leaves | never more than 2 in | [1] |
| Wood chips for weed suppression | 4 in | [4] |
| UK guidance | at least 5 cm, ideally 7.5 cm | [5] |
The full comparison, with what goes wrong at each extreme, is in the mulch depth guide. For curved or oddly shaped beds, see how to measure irregular areas.
Mulch rings around trees
A ring 6 ft across with a 1 ft bare center takes about 6.9 cu ft of mulch at 3 inches.
Use the Ring shape for a circle of mulch with a bare zone at the center. Keep mulch at least 4 inches away from the trunk; piling it against the trunk and root flare is among the most common causes of tree decline.[2] Clemson adds that mulch should stay 2–3 inches from woody stems and 6–12 inches from building walls.[1]
Example: a ring 6 ft across with a 1 ft bare circle at the trunk, mulched 3 inches deep, covers 27.5 sq ft and takes 6.9 cu ft, or 4 bags of 2 cu ft.
No mulch volcanoesA cone of mulch piled against the trunk is exactly the overmulching problem described above. Spread mulch flat and pull it back from the trunk before you measure the inner diameter.
Bags or bulk
Bagged mulch is commonly sold in 2 or 3 cubic foot bags.[3] A cubic yard is 13.5 bags of 2 cu ft or 9 bags of 3 cu ft (the bags per cubic yard chart covers other sizes). One brand's label for its 2 cu ft bag gives 12 sq ft at 2 inches, 8 sq ft at 3 inches and 6 sq ft at 4 inches,[6] exactly what the formula above predicts. In the UK, bark is sold in liters: one major brand packs landscape bark in 90 and 100 L bags and suggests 2.5–5 cm in borders.[8] Switch the calculator to meters for liter bags.
How much does a yard of mulch weigh?
About 243 lb dry and 473 lb fresh for a loose cubic yard of wood chips.
Much less than stone, and it depends heavily on moisture. EPA conversion factors put a loose cubic yard of dry wood chips at 243 lb and green (fresh, wet) chips at 473 lb.[7] That is about 144–281 kg per cubic meter. The calculator shows this range when you pick wood chip mulch. Other materials are compared in how much a cubic yard weighs.
Topping up every year
Organic mulch breaks down. Wood chips are usually gone within about two years, while pine needles and bark last roughly two to four.[1] Measure what is left before you top up, and calculate only the depth you need to add.
Bags or bulk mulch: same bed, both ways
A 200 sq ft bed at 3 inches needs 1.85 cubic yards of bulk mulch, which is 25 bags of 2 cu ft or 17 bags of 3 cu ft.
| Bed area | Cubic yards | 2 cu ft bags | 3 cu ft bags |
|---|---|---|---|
| 50 sq ft | 0.46 | 7 | 5 |
| 100 sq ft | 0.93 | 13 | 9 |
| 200 sq ft | 1.85 | 25 | 17 |
| 400 sq ft | 3.7 | 50 | 34 |
| 800 sq ft | 7.41 | 100 | 67 |
Common mulch mistakes
The most damaging mistake is piling mulch against tree trunks: overmulching and mulch on the root flare are among the most common causes of tree decline.[2]
- Spreading fine mulch too deep. Fine wood or bark mulch should stay at 2–3 inches; only coarse nuggets go to 4.[1]
- Piling grass clippings or leaves. Keep them to 2 inches or less.[1]
- Ignoring last year's mulch. Measure what is left and order only the depth you need to add.
- Mixing up bag sizes. A yard is 13.5 bags of 2 cu ft but only 9 of 3 cu ft.
- Measuring a tree ring as a full circle. Use the ring shape so the bare center around the trunk is left out.
Mulch for border beds
A border bed is the outer rectangle minus the inner one: a 40 × 20 ft yard with a 3 ft border bed is 800 − (34 × 14) = 324 sq ft, which at 3 inches is exactly 3 cubic yards, or 41 bags of 2 cu ft. Use the Border strip shape for these, and the Trapezoid shape for tapered beds: the average of the two parallel sides times the depth of the bed.
How much does a yard of mulch cost?
A yard of mulch costs your supplier's bulk price per yard, plus delivery. In bags, the same yard is 13.5 bags of 2 cu ft or 9 bags of 3 cu ft, so multiply the bag price by 13.5 or 9 to compare. Prices vary too much by region and mulch type to publish, so enter your own in the calculator's price fields and it shows both totals.
Frequently asked questions
How many bags of mulch do I need?
Multiply the area in square feet by the depth in inches and divide by 12 to get cubic feet. Divide by the bag size and round up. 100 sq ft at 3 inches is 25 cu ft, which is 13 bags of 2 cu ft or 9 bags of 3 cu ft.
How many square feet does a yard of mulch cover?
162 sq ft at 2 inches, 108 sq ft at 3 inches and 81 sq ft at 4 inches.
How deep should mulch be?
How many bags of mulch are in a yard?
13.5 bags of 2 cu ft, or 9 bags of 3 cu ft.
How much mulch for a tree ring?
A ring 6 ft across with a 1 ft bare center at 3 inches deep takes about 6.9 cu ft, or 4 bags of 2 cu ft.
Sources
- Mulch (HGIC 1604)
- Tree Care Basics: Proper Mulching Techniques
- How to Determine the Amount of Mulch Needed for a Garden Bed
- Mulching (CMG GardenNotes #245)
- Mulches and mulching
- Scotts Nature Scapes Colour Enhanced Mulch (product label coverage)
- Volume-to-Weight Conversion Factors
- Westland Landscape Bark (product specification)