Mulch Calculator

How to Calculate Mulch for Garden Beds?

Multiply the bed length by the width to get the area in square feet. Multiply the area by the desired depth (in feet) to get cubic feet. Divide by 27 to convert to cubic yards. A garden bed 20 feet long, 10 feet wide, and 3 inches deep needs 20 x 10 x 0.25 = 50 cubic feet = 1.85 cubic yards. The calculator above handles this conversion and shows results in both cubic yards (for bulk delivery) and number of 2-cubic-foot bags (for retail purchase), so you can choose whichever buying option makes sense for your project size.

How Deep Should Mulch Be?

Apply 2-3 inches of mulch for most garden beds and around trees and shrubs. This depth suppresses weeds, retains moisture, and moderates soil temperature effectively. Less than 2 inches allows weeds to push through and dries out quickly. More than 4 inches can suffocate plant roots and create moisture problems. Around tree trunks, keep mulch 3-6 inches away from the bark to prevent rot and pest habitat (the "mulch volcano" piled against trunks is one of the most damaging common landscaping practices). For playground surfaces, a 6-inch depth of engineered wood fiber provides adequate fall protection under play equipment.

What Types of Mulch Are Available?

Hardwood mulch (shredded bark from oak, maple, and other hardwoods) is the most popular landscape mulch. It knits together well, resists washing on slopes, and decomposes slowly over 1-2 years. Cedar mulch repels some insects naturally and lasts longer than hardwood. Pine bark mulch comes in nugget and shredded forms and is slightly acidic, benefiting acid-loving plants like azaleas and blueberries. Dyed mulch (black, red, brown) is hardwood colored with iron oxide or carbon-based dyes. Rubber mulch (from recycled tires) does not decompose and is used around playgrounds. Straw mulch is temporary, used in vegetable gardens and for erosion control on new seeding.

Bulk Mulch vs Bagged Mulch: Which Is Cheaper?

Bulk mulch costs $25-$50 per cubic yard delivered, depending on type and location. A 2-cubic-foot bag at a home center costs $3-$5, which equals $40-$67 per cubic yard (since one cubic yard equals 13.5 bags). Bulk delivery is nearly always cheaper for projects needing 2 or more cubic yards. One cubic yard of mulch covers about 100 square feet at 3 inches deep. A typical suburban home needs 3-8 cubic yards for all landscape beds. The break-even point is usually around 1.5-2 cubic yards: below that, bags are more convenient despite the premium; above that, bulk saves significant money.

How Often Should Mulch Be Replaced?

Most organic mulches need refreshing once per year. Hardwood and cedar mulch decompose over 12-18 months, losing volume and color. Rather than removing old mulch, add 1-2 inches of fresh mulch on top to restore the total depth to 3 inches. The decomposing bottom layer enriches the soil with organic matter, which is one of the key benefits of organic mulch. Dyed mulch fades faster in direct sun and may need a fresh layer every 6-12 months to maintain color. Rubber and stone mulches do not decompose and last indefinitely but do not improve soil quality.

How Much Does a Cubic Yard of Mulch Cover?

At 2 inches deep: 1 cubic yard covers 162 square feet. At 3 inches deep: 108 square feet. At 4 inches deep: 81 square feet. These coverage figures help you quickly estimate whether a bulk delivery will be enough. A standard landscaping truck delivers 2-5 cubic yards per load. For large properties, a dump truck delivers 10-15 cubic yards. Have the delivery dumped as close to the work area as possible, since moving mulch by wheelbarrow is the most time-consuming part of the job. One cubic yard fills about 9 standard wheelbarrow loads.

Benefits of Mulching Beyond Appearance

Mulch reduces water evaporation from soil by up to 70%, cutting irrigation needs significantly. It moderates soil temperature, keeping roots cooler in summer and warmer during early spring and late fall. Decomposing organic mulch adds nutrients and improves soil structure over time, encouraging beneficial earthworm and microbial activity. A 3-inch mulch layer blocks sunlight from reaching weed seeds, reducing weed germination by 80-90%. Mulch also prevents soil erosion during heavy rain and reduces soil compaction from foot traffic around plantings.

Mulch Installation Tips

Pull existing weeds and apply a pre-emergent herbicide before mulching for the best weed suppression. Edge garden beds with a shovel or power edger to create a clean boundary that keeps mulch out of the lawn. Spread mulch evenly to the desired depth using a garden rake. Taper mulch depth to zero where it meets plant stems and tree trunks. Water the bed after mulching to settle the material and begin moisture retention. For sloped beds where mulch tends to slide, use shredded hardwood rather than nuggets. The shredded fibers interlock and stay in place far better than round, smooth bark nuggets.

Frequently asked questions