Mulch Calculator: How Many Cubic Yards Do I Need?

The Formula

Length (ft) x Width (ft) x Depth (inches) / 324 = Cubic Yards

The 324 converts everything in one step: 27 cubic feet per yard times 12 inches per foot = 324.

Or if you prefer two steps: multiply length by width by depth in feet (divide inches by 12), then divide by 27.

A Real Example

Front yard bed: 40 feet long, 6 feet deep, mulched 3 inches thick.

40 x 6 x 3 / 324 = 2.22 cubic yards

You’d order 2.5 yards. Bulk mulch is sold in half-yard increments at most landscape suppliers.

Coverage Per Yard at Common Depths

One cubic yard covers:

• 2 inches deep: 162 sq ft
• 3 inches deep: 108 sq ft
• 4 inches deep: 81 sq ft
• 6 inches deep: 54 sq ft

Three inches is standard for most garden beds. It’s thick enough to suppress weeds and hold moisture but thin enough that perennials can push through. Two inches works for refreshing existing mulch that’s settled. Four inches is overkill for decorative beds but right for playground surfacing and paths.

Bags vs Bulk

A standard 2 cubic foot bag covers 8 sq ft at 3 inches. For our 240 sq ft front bed:

240 / 8 = 30 bags

At $4.50 per bag: $135.

Bulk mulch from a landscape supplier runs $25-45 per cubic yard. Our 2.5 yards: $62-$112 delivered.

Bags cost roughly double, sometimes more. They make sense for small jobs under half a yard, or if you don’t have anywhere for a dump truck to drop a pile. Everything else, buy bulk.

The break-even is usually around 1 cubic yard. Below that, the delivery fee ($40-75) eats into the savings. Above it, bulk wins every time.

How Much Fits in a Pickup Truck

A full-size pickup bed (6.5 feet) holds about 2 cubic yards heaped and about 1.3 yards level with the rails. A short bed (5.5 feet) holds about 1.5 yards heaped, 1 yard level.

But can your truck handle it? Mulch weighs 400-800 pounds per cubic yard depending on moisture. Dry hardwood mulch: about 500 lbs/yd. Wet mulch after a rain: 700-800 lbs/yd. Topsoil is heavier, around 2,000 lbs/yd.

A half-ton truck (F-150, Silverado 1500) has a payload capacity of 1,500-2,000 pounds depending on options. Two yards of dry mulch at 1,000 pounds total is fine. Two yards of wet topsoil at 4,000 pounds will break something.

Know your payload before you pull up to the loader.

Topsoil Math

Same formula. Topsoil is usually spread at 2-4 inches for lawn renovation, 6-8 inches for new garden beds, and 12 inches for raised beds.

A 10 x 4 raised bed filled 12 inches deep: 10 x 4 x 12 / 324 = 1.48 yards. But that’s all topsoil, which gets expensive. Most people fill the bottom 6 inches with a cheaper fill material (old logs, leaves, rough compost) and top it with 6 inches of good topsoil. That cuts your topsoil order in half.

Topsoil runs $20-50 per cubic yard for screened, $10-25 for unscreened. Four raised beds at 1.5 yards each: 6 yards at $35/yd = $210 delivered. Cheaper than the bagged stuff from the garden center by a wide margin.

Gravel and Stone

Same volume formula, different depths. Gravel driveways need 4-6 inches. A 12 x 60 foot driveway at 4 inches:

12 x 60 x 4 / 324 = 8.89 cubic yards

Gravel weighs about 2,800 lbs per cubic yard. Nine yards is over 25,000 pounds. That’s not a pickup truck job. That’s a dump truck delivery, and you’ll want a Bobcat to spread it unless you enjoy shoveling 12 tons by hand.

Pea gravel for a patio base: 2 inches is standard under pavers. A 15 x 20 patio: 15 x 20 x 2 / 324 = 1.85 yards.

Irregular Beds

Landscape beds are never rectangles. Break the bed into shapes you can measure. A kidney-shaped bed along the front of the house might be three rough rectangles: the straight section along the walkway, the curve around the tree, and the strip near the porch. Measure each, calculate separately, add them together.

Overestimate the width on curved sections. If the bed pinches to 4 feet at the narrowest and bulges to 8 feet around the tree, using the average (6 feet) will leave you short. Use the wider measurement and accept the leftover. Extra mulch keeps in a pile. Running out mid-job means another trip or another delivery fee.

Running the Numbers

SiteCalc has calculators for mulch, topsoil, and gravel that handle all of this. Punch in your bed dimensions, pick a depth, and it gives you cubic yards, number of bags, and cost. The budget calculator works backward too: tell it you’ve got $200 for mulch at $35 a yard, and it tells you how many square feet of bed that covers at 3 inches. Useful when you’re pricing a landscaping job against a fixed budget.

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