Measure your garden beds to find the square footage

The first step is to measure the area you plan to cover. Use a measuring tape to find the length and width of each bed in feet, then multiply those two numbers together. If your bed is 10 feet long and 4 feet wide, that's 40 square feet. Do this for every bed you want to mulch, then add all the numbers together to get your total square footage.

For oddly shaped beds, break them into rectangles and triangles. Measure each section separately, calculate the area, and add them up. A triangle's area is half the base times the height, so a triangular section 6 feet across and 3 feet deep would be 9 square feet (6 × 3 ÷ 2). This method works for curved beds too—just approximate the curve as a series of smaller rectangles.

Write down your total square footage before moving to the next step. You'll use this number to calculate how much mulch to order.

Key Takeaways

  • Multiply the length and width of each bed in feet to find square footage, then add all beds together for your total.
  • A depth of 2 to 3 inches is standard for most mulch applications—2 inches for annual refreshes and 3 inches for new beds or weed control.
  • Divide your total square footage by 100 to find how many cubic yards you need at 2 inches deep, or by 67 for 3 inches deep.
  • Mulch settles and breaks down over time, so order 10 to 15 percent extra to account for settling in the first few weeks.
  • Bulk mulch is usually cheaper per cubic yard than bagged mulch, but bagged mulch works better for small areas under 100 square feet.

Decide on the depth you want

The depth of mulch affects how well it suppresses weeds and retains moisture. A 2-inch depth is the standard for refreshing existing beds each year. It's deep enough to block most weeds and hold moisture without piling mulch against tree trunks or plant stems, which can cause rot.

Use 3 inches if you're mulching a new bed, dealing with persistent weeds, or want maximum moisture retention. Three inches takes longer to break down and gives you better weed control, but it costs more and requires more careful placement around plants. Never go deeper than 4 inches—mulch that thick can trap moisture and create conditions for fungal growth and pest problems.

If you're refreshing an existing bed that already has mulch, measure how much is left. If there's still 1 to 2 inches, you only need to add 1 inch more to reach the 2 to 3-inch target.

Convert square footage to cubic yards

Mulch is sold by the cubic yard, not by square feet, so you need to convert. The math is straightforward: divide your total square footage by 100 for a 2-inch depth, or by 67 for a 3-inch depth. These numbers account for the fact that one cubic yard of mulch covers 100 square feet at 2 inches or 67 square feet at 3 inches.

Here's an example: if your total square footage is 400 square feet and you want 2 inches of mulch, divide 400 by 100 to get 4 cubic yards. If you want 3 inches instead, divide 400 by 67 to get about 6 cubic yards.

Round up to the nearest half cubic yard when you place your order. It's better to have a little left over than to run short partway through the job. Leftover mulch can be stored in a dry spot and used for touch-ups later in the season.

Account for mulch settling and breakdown

Mulch compacts and breaks down over time, especially in the first few weeks after you spread it. Wood-based mulches settle by 10 to 15 percent as they absorb water and begin to decompose. This means your 3-inch layer may drop to 2.5 inches within a month.

To account for this, add 10 to 15 percent to your cubic yard total before ordering. If your calculation came to 6 cubic yards, order 6.6 to 6.9 cubic yards instead. This extra amount ensures your beds stay at the depth you want through the season without requiring an when ready second process.

Mulch also breaks down faster in warm, wet climates and slower in cool, dry ones. If you live somewhere hot and humid, lean toward the higher end of the 10 to 15 percent buffer. In drier regions, 10 percent is usually enough.

Choose between bulk and bagged mulch

Bulk mulch is delivered by the cubic yard and costs less per unit—typically $25 to $50 per cubic yard depending on the type and your location. It's the better choice for beds totaling more than 100 square feet. You'll need a place for the delivery truck to drop the pile, and you'll handle the spreading yourself.

Bagged mulch comes in 2 to 3 cubic foot bags and costs more per cubic yard but works better for small areas, tight spaces, or if you don't have room for a bulk delivery. One bag covers roughly 8 to 12 square feet at 2 to 3 inches deep. For a 100 square-foot bed at 2 inches, you'd need about 10 to 12 bags.

If you're ordering bulk mulch, confirm with the supplier that they can deliver to your address and that you have a clear spot for the pile. Some suppliers charge extra for delivery outside their service area or for difficult access.

Common mistakes to avoid

The most common error is piling mulch against tree trunks and plant stems. This traps moisture and creates an entry point for pests and disease. Keep mulch at least 3 to 4 inches away from the base of any tree or shrub, creating a small ring of bare soil around the stem.

Another mistake is underestimating square footage by not measuring carefully. Eyeballing a bed often leads to ordering too little, and you'll either have to place a second order or spread the mulch thinner than intended. Spend the extra 10 minutes with a tape measure—it saves money and frustration.

Don't forget to subtract the area of any hardscape, large rocks, or plants that are already in the bed. If your bed is 100 square feet but has a 20-square-foot patio in the middle, you only need mulch for 80 square feet. These details add up, especially across multiple beds.

Frequently Asked Questions

How much mulch do I need for a 200 square foot bed?

At 2 inches deep, divide 200 by 100 to get 2 cubic yards. At 3 inches deep, divide 200 by 67 to get about 3 cubic yards. Add 10 to 15 percent for settling, so order 2.2 to 2.3 cubic yards for 2 inches, or 3.3 to 3.45 cubic yards for 3 inches.

Can I use the same calculation for wood chips and bark mulch?

Yes, the square footage to cubic yard conversion works for all common mulch types—wood chips, shredded bark, and hardwood mulch all cover roughly the same area per cubic yard. The settling rate may vary slightly by type, but 10 to 15 percent is a safe estimate for all of them.

What if I have an irregularly shaped bed?

Break the bed into smaller rectangles and triangles, measure each section, and add the areas together. For a bed that's roughly circular, measure the radius (distance from center to edge), multiply it by itself, then multiply by 3.14 to get the area in square feet.

Should I measure mulch depth before or after spreading?

Measure after spreading and watering lightly, since mulch compacts when wet. Stick a ruler or measuring stick into the mulch at several spots around the bed and average the depths. This tells you whether you've reached your target depth.

How often do I need to recalculate and add more mulch?

Most mulch needs refreshing once a year, usually in spring. If you started with 3 inches and it's settled to 2 inches by the following spring, add 1 inch more. This typically requires about one-third of the original amount you ordered.