Calculate mulch by measuring your garden area and deciding on depth
The amount of mulch you need depends on two things: the square footage of the area you want to cover and how deep you want the mulch layer to be. Most gardeners spread mulch between 2 and 4 inches deep. A 2-inch layer works for established beds where you're topping up; 3 to 4 inches is standard for new beds or areas with heavy weed pressure. Once you know your square footage and your target depth, a straightforward calculation tells you the cubic yards to order.
Mulch is sold by the cubic yard, not by weight or bag count. One cubic yard covers roughly 100 to 150 square feet at a 2-inch depth, 65 to 100 square feet at a 3-inch depth, and 50 to 75 square feet at a 4-inch depth. The variation depends on how densely the mulch settles—wood chips settle differently than shredded bark or compost.
Key Takeaways
- Measure your garden bed length and width in feet, multiply them together to get square footage, then divide by the coverage rate for your chosen depth.
- A 2-inch depth is enough for maintenance; 3 to 4 inches is standard for new beds or heavy weed control.
- One cubic yard of mulch covers roughly 100 square feet at 2 inches, 80 square feet at 3 inches, and 60 square feet at 4 inches.
- Irregular or curved beds require you to estimate the area by breaking the shape into rectangles or using the average-width method.
- Order 10 to 15 percent extra to account for settling and uneven ground.
Measure your garden bed in feet
Start by measuring the length and width of each bed in feet. Use a tape measure or a measuring wheel if your beds are large. If you have multiple beds, measure each one separately—don't try to estimate a total.
For rectangular beds, multiply length by width. A bed that is 10 feet long and 4 feet wide is 40 square feet. For oddly shaped beds, break them into rectangles. A bed shaped like an L can be split into two rectangles: measure the top section and the bottom section separately, then add the totals together.
For curved or circular beds, measure the average width and length. If a curved bed is roughly 8 feet long but varies from 3 to 5 feet wide, use 4 feet as your average width. Multiply 8 by 4 to get 32 square feet. This method gives you a close estimate without needing to calculate a true circle.
Divide your square footage by the coverage rate
Once you have your total square footage, choose your target depth and use the coverage rate for that depth. The chart below shows how many square feet one cubic yard covers at different depths.
| Depth | Square feet per cubic yard |
|---|---|
| 2 inches | 100–150 sq ft |
| 3 inches | 65–100 sq ft |
| 4 inches | 50–75 sq ft |
Use the middle of the range for a realistic estimate. For a 3-inch depth, use 80 square feet per cubic yard. If your bed is 200 square feet, divide 200 by 80 to get 2.5 cubic yards. Round up to 3 cubic yards to account for settling.
If you prefer a formula: multiply your square footage by the depth in inches, then divide by 324. This gives you cubic yards directly. For example: (200 sq ft × 3 inches) ÷ 324 = 1.85 cubic yards, which rounds to 2 cubic yards. The slight difference from the chart method comes down to how tightly mulch compacts during delivery and spreading.
Account for settling and uneven ground
Mulch settles over time as it breaks down and as rain compacts it. Order 10 to 15 percent extra to keep your beds at the depth you want after the first few weeks. If your calculation says you need 3 cubic yards, order 3.3 to 3.5 cubic yards instead.
Uneven ground also affects how much mulch you'll need. If your bed has low spots or slopes, those areas will hold more mulch than level sections. Walk your bed before you order and note any dips. If the ground is very uneven, add another 10 percent to your total.
Common mistakes that waste mulch or leave bare spots
The most common mistake is measuring only the visible bed area and forgetting to account for depth. A 100-square-foot bed at 2 inches needs less mulch than the same bed at 4 inches—but many people order the same amount regardless. Always decide on depth first.
Another mistake is not measuring at all and guessing based on how the bed looks. A bed that looks "medium-sized" can be anywhere from 50 to 200 square feet. Guessing almost always results in either too little mulch (leaving bare spots) or too much (wasting money and creating a fire hazard if the layer is thicker than 4 inches).
Forgetting to subtract hardscape also wastes money. If your bed has a tree, a stepping stone, or a garden edging, measure around those obstacles. A 10-foot by 10-foot bed with a 2-foot-diameter tree in the middle is not 100 square feet—it's roughly 97 square feet. The difference is small in this case, but large beds with multiple trees or structures can save you a cubic yard or more.
Adjust your order for mulch type and settling rate
Different mulch types settle at different rates. Wood chips (larger, chunkier pieces) settle less than shredded bark or finely ground mulch. If you're ordering wood chips, you may need slightly less extra. If you're ordering fine mulch or compost, add the full 15 percent.
Mulch delivered loose in a truck settles more than mulch that comes in bags. Loose mulch is compressed during transport and settles further when you spread it. Bagged mulch is fluffier and settles less. If you're buying loose mulch, add 15 percent. If you're buying bags, 10 percent is usually enough.
Wet mulch weighs more and compacts faster than dry mulch. If your delivery arrives after rain, expect more settling. Dry mulch from a summer delivery will settle less in the short term but may shift more if heavy rain comes later.
When to order mulch and how to place your order
Order mulch in spring (March to May) or fall (September to October) when most landscape suppliers have stock and delivery is reliable. Summer orders can take longer because demand is high. Winter orders may be delayed by weather.
Call local landscape supply yards or garden centers and ask for a quote. Tell them your square footage and target depth, and they can calculate cubic yards for you. Many suppliers deliver for a flat fee or charge per cubic yard. Delivery usually takes one to three days after you order.
If you're buying bagged mulch from a garden center or big-box store, calculate how many bags you need. Most bags are 2 or 3 cubic feet. One cubic yard equals 27 cubic feet, so you'll need 9 to 13 bags per cubic yard depending on bag size. Bagged mulch costs more per cubic yard but works well for small beds or if you don't have a place for a truck to deliver loose mulch.
Frequently Asked Questions
Can I use the same calculation for wood chips, bark, and compost?
Yes, the square footage and depth method works for all mulch types. The coverage rate (square feet per cubic yard) varies slightly because different materials settle differently, but using 80 square feet per cubic yard at 3 inches is a safe middle estimate for any type. If you're unsure, ask your supplier what coverage rate they recommend for the specific product you're ordering.
What if my bed is very small, like just a few square feet?
For beds under 50 square feet, bagged mulch is usually cheaper and easier than ordering a full cubic yard. A single cubic yard is overkill for a small space and you'll have leftover mulch. Buy bags instead and store any extra in a dry place for next year's top-up.
How do I measure a circular or oval bed?
For a circle, measure the diameter (the distance across the widest point) and divide by 2 to get the radius. Then use the formula: radius × radius × 3.14 = square feet. For an oval, measure the long axis and short axis, divide each by 2, then multiply them together and multiply by 3.14. For irregular shapes, the average-width method (length × average width) is close enough and easier to do by hand.
Should I remove old mulch before spreading new mulch?
If the old mulch is still in good condition and less than 2 inches deep, you can spread new mulch on top. If it's matted, moldy, or thicker than 3 inches, rake it back or remove it. Spreading new mulch over old mulch that's too thick can create a water-resistant layer. When you remove old mulch, you'll need less new mulch—measure only the bare ground you're covering.
What depth should I use if I'm trying to prevent weeds?
A 3 to 4-inch depth is most effective for weed suppression. At 2 inches, weed seeds can still push through. At 4 inches, you're blocking most light and creating a barrier that's hard for weeds to penetrate. Keep the mulch a few inches away from tree trunks and plant stems to prevent rot and pest problems.