Mulch Calculator

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How to Use the Mulch Calculator

1. 1

   Choose the bed shape

   Select Rectangle, Circle or Triangle. For irregular beds, split them into simple shapes and add the results together.

2. 2

   Pick units and enter dimensions

   Choose feet, yards or meters, then enter the length and width, the diameter, or the base and height of the triangle.

3. 3

   Set the mulch depth

   Type the depth in inches or tap a preset: 2, 3, 4 or 6 inches. Three inches is the default. Depth stays in inches even if you measure the bed in meters.

4. 4

   Read the results

   The calculator shows area, cubic yards and 2 cu ft bags. If you enter a price per cubic yard, it also shows an estimated cost.

How the mulch calculator works

The area is calculated in square feet first. Yards are multiplied by 3 and meters by 3.28084. Rectangles are length times width, circles are pi times the radius squared, and triangles are half the base times the height.

Multiplying the area by the depth in feet (inches divided by 12) gives cubic feet. Dividing by 27 gives cubic yards, the unit bulk mulch is sold in. Bags are based on the common 2 cubic foot bag and always rounded up to a whole bag. No extra for settling is added, and the cost is cubic yards times your price per yard.

Cubic feet = area sq ft × (depth in ÷ 12)
Cubic yards = cubic feet ÷ 27
2 cu ft bags = cubic feet ÷ 2, rounded up
(3 cu ft bags = cubic feet ÷ 3, rounded up)

Worked example: a 20 x 4 ft bed at 3 inches

For a tree ring 6 ft across at the same depth, the area is 28.3 sq ft, which needs 7.1 cubic feet, or 4 bags.

• Area: 20 × 4 = 80 sq ft.
• Depth in feet: 3 ÷ 12 = 0.25 ft.
• Volume: 80 × 0.25 = 20 cubic feet.
• Cubic yards: 20 ÷ 27 = 0.74 cubic yards.
• Bags: 20 ÷ 2 = 10 bags of 2 cu ft.
• With about 10% extra for settling and edges: 22 cubic feet, or 11 bags.

Mulch needed for 100 to 1,000 sq ft

Bag counts are rounded up and include no extra. Add about 10% for settling and edges. Not sure of your square footage? Measure each bed with the square footage calculator and add them up.

Mulch coverage by depth

Shortcut: one cubic yard covers 324 ÷ depth in inches square feet. In metric, 1 m³ spread 7.5 cm deep (about 3 in) covers 13.3 m².

How deep should mulch be?

• Refreshing existing mulch: 1 to 2 inches is usually enough to restore color and cover.
• New beds and weed control: 2 to 3 inches is a common recommendation, with 3 inches doing a better job of blocking light to weed seeds.
• Coarse bark or wood chips on paths and play areas can go deeper, since they settle and break down more slowly.
• Keep mulch a few inches away from tree trunks and plant stems. Piling it against bark holds moisture there and can encourage rot and pests.

Edge cases that change the amount

• Existing mulch: measure what is already there with a ruler and only add the difference. Topping a bed that still has 1.5 in up to 3 in needs half the mulch of a bare bed.
• Plants and shrubs: the area under large shrubs is not mulched, so subtract big clumps or you will over-order. Small perennials can be ignored.
• Slopes and banks: mulch slides downhill and washes out in heavy rain. Shredded bark knits together better than nuggets on slopes, and you may need a little extra for the lower edge.
• Fresh vs settled: newly spread mulch is fluffy and settles as it dries and decomposes, which is why the 10% extra matters on new beds.
• Bag sizes: most bags are 2 cu ft, some 3 cu ft, and a few 1.5 cu ft. Divide the cubic feet result by whatever is printed on the bag.

Bags or bulk, and other tips

• A cubic yard equals 13.5 bags of 2 cu ft or 9 bags of 3 cu ft. Once a project needs more than a couple of cubic yards, bulk delivery is often cheaper per yard, but prices and delivery fees vary by region, so compare both.
• The cost estimate multiplies the cubic yards by your price per yard. For bagged mulch, multiply the bag count by the bag price instead.
• Measure beds after edging and removing weeds, not before, so you are covering the real planted area.
• Building a new raised bed or leveling low spots? Fill with soil first using the topsoil calculator, then mulch on top. For stone instead of wood mulch, use the gravel calculator, which estimates weight in tons.
• For large properties (several thousand square feet), landscapers with a mulch blower truck can spread bulk mulch quickly and evenly; it is worth a quote when the bag count runs into the hundreds.

Features

• Calculate by area and depth
• Results in cubic yards/bags
• Multiple bed shapes
• Cost estimation

Frequently Asked Questions