Rectangular Bed Mulch Calculator
Calculate mulch for any rectangular bed by length x width x depth. Output in bags and yards.
Rectangular Bed Mulch Calculator
Length x width x depth to bags and yards
Standard Bed Sizes
A rectangular bed is the easiest shape to mulch because the area is simply length times width. The calculator multiplies that area by depth in inches and divides by 324 for cubic yards. A 20 x 10 ft bed at 3 inches deep needs 1.85 cubic yards or 25 bags of 2 cubic feet. One cubic yard covers 108 sq ft at 3 inches, 162 sq ft at 2 inches, and 81 sq ft at 4 inches. The table below lists mulch for the most common rectangular bed sizes at the standard 3 inch depth. Measure to the nearest half foot for an accurate result.
| Bed Size | Cubic Yards (3") | 2 cu ft Bags |
|---|---|---|
| 4 x 8 ft (32 sq ft) | 0.30 yd³ | 4 bags |
| 10 x 10 ft (100 sq ft) | 0.93 yd³ | 13 bags |
| 20 x 10 ft (200 sq ft) | 1.85 yd³ | 25 bags |
| 30 x 15 ft (450 sq ft) | 4.17 yd³ | 57 bags |
Multi-Section Beds
An L-shaped or stepped bed is just two or more rectangles. Split the bed at the corner, measure each rectangle, and calculate its cubic yards separately. Then add the totals and apply a 10 percent buffer. For example, a 12 x 4 ft section plus an 8 x 4 ft section is 48 sq ft plus 32 sq ft, or 80 sq ft total. At 3 inches that is 0.74 cubic yards. This split method works for any number of sections and matches how the National Association of Landscape Professionals (NALP) measures complex beds in the field.
How Much Mulch Do I Need
The amount of mulch depends on bed size and depth. The formula is Length x Width x Depth in inches divided by 324 for cubic yards. For bags, divide cubic feet by the bag size: 13.5 bags of 2 cubic feet fill one cubic yard. A rectangular bed at the standard 3 inch depth is the most common landscape job. The International Society of Arboriculture (ISA) sets 2 to 4 inches as the universal depth range. Always round bags up to the next whole unit because partial bags are not sold.
How do I measure a rectangular bed?
Measure a rectangular bed with a tape along the longest side for the length and across for the width. Record both to the nearest half foot. Multiply them for the square footage. If the bed has a slight curve on one edge, measure the average width at three points. Enter the dimensions and depth into the calculator for instant cubic yards and bags.
How deep should rectangular bed mulch be?
Rectangular beds need 2 to 3 inches of mulch. Annual flower beds take 2 inches so shallow roots breathe. Shrub and perennial beds take 3 inches for stronger weed control. Heavy weed pressure justifies 4 inches. Keep mulch 2 inches off plant stems and never exceed 4 inches because deep mulch suffocates roots.
Why Rectangular Beds Are the Easiest to Calculate
Rectangular beds are the easiest shape to calculate because the area is a simple length times width. There is no pi, no half-base-times-height, and no averaging of curves. This makes the rectangle the default shape for raised beds, foundation borders, and vegetable plots. If your bed is close to rectangular with a slightly wavy edge, treat it as a rectangle using the average width and you will land within 10 percent of the true area.
The rectangle also scales cleanly for ordering. Double the length and you double the mulch. This linear relationship makes it easy to plan multiple identical beds, since you just multiply one bed's cubic yards by the number of beds. A row of four 10 by 4 ft beds at 3 inches is four times 0.37 cubic yards, or about 1.5 cubic yards total. Add the 10 percent buffer the National Association of Landscape Professionals (NALP) recommends, then round bags up. For any bed with a true curve or circle, switch to the matching shape calculator for an accurate count.
FAQ
Multiply length by width by depth in inches, then divide by 324 for cubic yards. A 20 x 10 ft bed at 3 inches needs 1.85 cubic yards or 25 bags of 2 cubic feet.
Cubic Yards = Length x Width x Depth in inches / 324. Area is length times width. One cubic yard covers 108 sq ft at 3 inches deep.
A 10 x 10 ft bed at 3 inches deep needs 0.93 cubic yards or 13 bags of 2 cubic feet. At 2 inches it needs 9 bags. Round up to the next whole bag.
Split an L-shaped bed into separate rectangles. Calculate each, then add the cubic yards together. Add 10 percent buffer to the combined total.
Rectangular beds need 2 to 3 inches. Use 2 inches for annuals and 3 inches for shrubs and perennials. Keep mulch 2 inches off plant stems.
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