Mulch
calculator.
Find how much mulch, compost or topsoil to buy for a bed or a ring around a tree, in cubic yards and whole bags. Compare the cost of bags with bulk delivery, and check your depth against university extension guidance.
200 sq ft of mulch at 3 in deep takes 1.85 cubic yards (50 cu ft), or 25 bags of 2 cu ft.
- Bags of 2 cu ft
- 25
- Bags of 3 cu ft
- 17
- Volume
- 1.85 cu yd · 50.00 cu ft · 1.42 m³
- Area
- 200 sq ft · 18.58 m²
- One cubic yard covers
- 108 sq ft at 3 in
volume = 200 sq ft × 3 in ÷ 12 = 50 cu ft ÷ 27 = 1.85185 cu yd
bags = ⌈50 cu ft ÷ 2 cu ft⌉ = 25Square feet, inches,
then bags.
- Volume = area × depth. Square feet × depth in inches ÷ 12 = cubic feet; cubic feet ÷ 27 = cubic yards. One cubic yard covers 324 sq ft at 1 inch deep.
- Bags = volume ÷ bag size, rounded up to a whole bag. Bag sizes are the loose volume printed on the bag; 1 cu ft = 28.317 liters.
- A tree ring is the circle out to the outer diameter minus the bare circle you keep clear around the trunk.
- Nothing is added for settling or uneven beds unless you enter an extra percentage. Depth guidance is from Clemson and University of Maryland Extension and is advice, not a rule.
How do you calculate how much mulch you need?
Multiply the bed's area in square feet by the depth in inches, then divide by 324 to get cubic yards. Clemson Cooperative Extension gives this rule because one cubic yard (27 cu ft) spread 1 inch deep covers 324 sq ft. A 20 × 10 ft bed is 200 sq ft; at 3 inches it needs 200 × 3 ÷ 324 = 1.85 cubic yards, or 50 cu ft.
cubic yards = area (sq ft) × depth (in) ÷ 324
cubic feet = area (sq ft) × depth (in) ÷ 12How many bags of mulch do I need?
Divide the cubic feet by the bag size and round up. The 200 sq ft bed at 3 inches needs 50 cu ft: 50 ÷ 2 = 25 bags of 2 cu ft, or 50 ÷ 3 = 16.7, so 17 bags of 3 cu ft. A cubic yard is 13.5 bags of 2 cu ft (buy 14) or exactly 9 bags of 3 cu ft. Metric bags are sold in liters: 1 m³ is 1,000 L, or 20 bags of 50 L.
bags = ⌈cubic feet ÷ bag size (cu ft)⌉How deep should mulch be?
University of Maryland Extension says to keep mulch shallow, from 1 to 3 inches. Clemson Extension says fine-textured wood and bark mulch should be no more than 2 to 3 inches deep, coarse mulch such as pine bark nuggets can be as deep as 4 inches, and grass clippings or shredded leaves no deeper than 2 inches, because too much fine mulch can suffocate roots.
Keep mulch off the trunk: Clemson says 2 to 3 inches away from the stems of woody plants, and Maryland about 3 inches from tree trunks. The calculator notes when your depth is outside this guidance.
How much mulch for a tree ring?
Work out the area of the ring and leave out the bare circle around the trunk. A ring 6 ft across with a 1 ft bare circle is π ÷ 4 × (6² − 1²) = 27.5 sq ft. At 3 inches that is 6.87 cu ft, or 4 bags of 2 cu ft (3 of 3 cu ft).
ring area = π ÷ 4 × (outer diameter² − bare diameter²)Is bulk mulch cheaper than bags?
Compare the two at your prices: bags cost the bag count × the bag price, and bulk costs cubic yards × the price per yard. For 1,000 sq ft at 2 inches with 10% extra (6.79 cu yd), 92 bags of 2 cu ft at $4 each is $368.00, while bulk at $35 per cubic yard is $237.65. Bulk deliveries often add a delivery fee or minimum order, which the calculator does not include.
Worked examples.
A flower bed
A 20 × 10 ft bed with 3 inches of mulch.
1.85 cu yd (50 cu ft): 25 bags of 2 cu ft, or 17 of 3 cu ft.
Load this exampleClemson's rule of thumb
324 sq ft at 1 inch, sold in 3 cu ft bags.
1.00 cu yd: 9 bags of 3 cu ft (14 of 2 cu ft).
Load this exampleRing around a tree
A ring 6 ft across with a 1 ft bare circle at the trunk, 3 inches deep.
0.25 cu yd (6.87 cu ft): 4 bags of 2 cu ft.
Load this exampleMetric bed in 50 L bags
A 4 × 2.5 m bed, 7.5 cm deep, using 50-liter bags.
0.75 m³ (0.98 cubic yards): 15 bags of 50 L.
Load this exampleBags or bulk for a large yard
1,000 sq ft at 2 inches with 10% extra; bags $4 each, bulk $35 per cubic yard.
6.79 cu yd: 92 bags cost $368.00, bulk $237.65.
Load this exampleCompost top layer
The same 20 × 10 ft bed with a 1-inch layer of compost.
0.62 cu yd (16.67 cu ft): 9 bags of 2 cu ft.
Load this exampleWhat this calculator
does not do.
- Beds are treated as flat with an even depth. Slopes, edging and uneven ground change the real amount; add an extra percentage.
- Bag counts use the volume printed on the bag. Mulch can settle after spreading and suppliers measure bulk loads in their own ways, so a top-up later is common.
- Depth guidance comes from two extension services and is general advice for landscape beds, not a rule for every plant, slope or climate.
- Prices are your own inputs. Delivery fees, minimum bulk orders and tax are not included.
Common questions.
How many square feet does a yard of mulch cover?
324 sq ft at 1 inch, 162 at 2 inches, 108 at 3 inches and 81 at 4 inches: divide 324 by the depth in inches.
How many bags of mulch are in a yard?
13.5 bags of 2 cu ft (buy 14) or 9 bags of 3 cu ft, because a cubic yard is 27 cu ft.
How much mulch do I need for 100 square feet?
At 3 inches, 100 × 3 ÷ 12 = 25 cu ft, or 0.93 cubic yards: 13 bags of 2 cu ft or 9 bags of 3 cu ft.
Can I use this for topsoil or compost?
Yes. Volume and bag counts work the same way for any loose material. For compost used as a mulch, University of Maryland Extension suggests about a 1-inch layer.
Should mulch touch the tree trunk?
No. Extension guides say to keep it a few inches away: 2 to 3 inches from woody stems (Clemson) and about 3 inches from trunks (Maryland).
- Clemson Cooperative Extension, Home & Garden Information Center: Mulch (HGIC 1604) — 324 sq ft per cubic yard at 1 inch; depth by mulch texture; keep 2–3 in from stems
- University of Maryland Extension: Mulching Trees and Shrubs — keep mulch 1 to 3 inches; about 1 inch of compost; about 3 inches from trunks
Area comes from the bed shape (rectangle, circle, tree ring or a known area) and is multiplied by depth to give volume in cubic meters with exact unit definitions (1 ft = 0.3048 m), then converted to cubic yards, cubic feet and liters. Bags are rounded up, with a tiny tolerance so that an exact fit such as 750 L in 50 L bags gives 15, not 16. Tests check hand-worked vectors, Clemson's 324 sq ft rule, 300 random cases for unit independence and monotonic bag counts, validation of every input, and the examples on this page.
Built and reviewed by CalculatorLab against the sources above; every worked example on this page is re-checked by our automated test suite before each release. How we build and check calculators. Found a problem? Tell us.