Measure your garden beds and multiply length by width

To find out how much bark mulch to buy, measure the length and width of each garden bed in feet, then multiply those two numbers together. That gives you the square footage of the bed. If your bed is irregularly shaped, break it into rectangles, calculate each one separately, and add them together.

Once you have the total square footage, decide how deep you want the mulch layer. Most gardeners use 2 to 3 inches. Bark mulch settles over time, so if you want it to stay at 3 inches through the growing season, you may want to start at 3.5 or 4 inches. Write down your target depth — you will need it for the next step.

Key Takeaways

  • Multiply the length and width of each bed in feet to get square footage, then add all beds together for your total.
  • A 2- to 3-inch depth is standard; account for settling by starting slightly deeper if you want consistent coverage through the season.
  • Divide your total square footage by the coverage rate on the mulch bag (usually 8 to 10 square feet per cubic yard) to find how many cubic yards you need.
  • Bark mulch is sold by the cubic yard, not by the bag, at most landscape suppliers, so ask for the price per cubic yard before ordering.
  • Order 10 to 15 percent extra to account for settling, uneven ground, and the space taken up by existing plants.

Convert square footage to cubic yards using the coverage rate

Bark mulch bags and bulk suppliers list a coverage rate — the number of square feet that one cubic yard of mulch will cover at a standard depth, usually 2 inches. Most bark mulch covers 8 to 10 square feet per cubic yard at 2 inches deep. Check the bag or ask the supplier what their coverage rate is; it varies slightly by bark size and density.

To find how many cubic yards you need, divide your total square footage by the coverage rate. For example, if you have 200 square feet of bed and the mulch covers 10 square feet per cubic yard, you need 200 ÷ 10 = 20 cubic yards. If you want the mulch 3 inches deep instead of 2, you will need about 50 percent more — in this case, 30 cubic yards — because the same volume of mulch spreads thinner.

The math is simpler if you use this rule of thumb: one cubic yard of mulch covers roughly 100 to 150 square feet at 2 inches deep, depending on bark size. Finer bark (smaller pieces) covers more area; coarser bark covers less. Ask your supplier which end of that range applies to their product.

Account for settling and uneven ground

Bark mulch compacts and settles as it breaks down and as rain and foot traffic work it into the soil. A layer that starts at 3 inches may drop to 2 inches or less within a few months. If you want consistent coverage through the season, order 10 to 15 percent extra mulch to top up the beds later, or start with a slightly deeper layer than you think you need.

Also add a small buffer for uneven ground and existing plants. If your beds have slopes, low spots, or tree roots, you will use more mulch in some places than others. Shrubs and perennials already in the bed take up space, so the actual ground area you are covering is smaller than the bed's total square footage. A 10 to 15 percent cushion accounts for both.

Understand cubic yards and how mulch is sold

Bark mulch is measured in cubic yards, not bags or tons. One cubic yard is a cube 3 feet long, 3 feet wide, and 3 feet tall — that is 27 cubic feet. A standard mulch bag holds about 2 to 3 cubic feet, so one cubic yard is roughly 9 to 13 bags, depending on the bag size.

Most landscape suppliers and garden centers sell mulch by the cubic yard in bulk. You can order it delivered in a truck, or you can rent a pickup and load it yourself. Bagged mulch is available at garden centers and hardware stores, but it costs more per cubic yard than bulk mulch. If you need more than 5 or 6 cubic yards, bulk delivery is usually cheaper and saves you the work of carrying bags.

Work through a real example

Say you have three garden beds: one that is 10 feet long and 4 feet wide, one that is 8 feet by 6 feet, and one that is 12 feet by 3 feet. Calculate each one: (10 × 4) + (8 × 6) + (12 × 3) = 40 + 48 + 36 = 124 square feet total.

You want the mulch 2.5 inches deep. The mulch you are looking at covers 10 square feet per cubic yard at 2 inches. At 2.5 inches, it will cover less — roughly 8 square feet per cubic yard. Divide 124 by 8 to get 15.5 cubic yards. Add 15 percent for settling and uneven ground: 15.5 × 1.15 = 17.8, so order 18 cubic yards.

If you were buying bags instead, and each bag holds 2.5 cubic feet, you would need 18 × 27 ÷ 2.5 = about 195 bags. That is why bulk delivery makes sense for anything larger than a small bed.

Check your math before you order

Before you place an order, write down your numbers and walk through them one more time. Write down the square footage of each bed, your target depth, the coverage rate the supplier gave you, and your final cubic yardage. If the number seems very large or very small compared to what you expected, ask the supplier to double-check the coverage rate — that is where most mistakes happen.

Also ask whether the supplier's coverage rate assumes the mulch is spread evenly and compacted, or loose. Loose mulch takes up more volume, so the same cubic yard will cover more area. If you are spreading it yourself, it will settle and compress over time, so you may want to start with slightly more than the calculation suggests.

Frequently Asked Questions

Do I need to measure every single bed, or can I estimate?

Measure the beds you are actually mulching. Estimation usually leads to ordering too little or too much. A 50-foot tape measure costs a few dollars and takes 10 minutes to use. If a bed is an odd shape, sketch it on paper, break it into rectangles, and measure each one.

What if my beds are on a slope?

Measure the length and width as if the bed were flat on the ground, not along the slope. The square footage is the same either way. You may use slightly more mulch on a slope because it settles faster, so add an extra 10 to 20 percent to your order.

Can I use the same calculation for wood chips or shredded hardwood?

Yes, the math is identical. Coverage rates vary by product — ask the supplier for the rate specific to what you are buying. Finer materials cover more area; coarser ones cover less. The depth recommendation is also the same: 2 to 3 inches for most purposes.

How much does a cubic yard of bark mulch weigh?

Bark mulch typically weighs 400 to 600 pounds per cubic yard, depending on moisture content and bark size. Wet mulch is heavier than dry. If you are renting a truck, check the weight limit and ask the supplier how much their mulch weighs before you load it.

Should I put landscape fabric under the mulch?

That is a separate decision from calculating coverage. Landscape fabric goes down before the mulch and does not change how much mulch you need. The calculation stays the same whether you use fabric or not.