Measure the area you want to cover, then multiply by depth to find cubic yards
A yard of mulch is a cubic yard—a block of mulch three feet long, three feet wide, and three feet deep. To know how much you need, measure the length and width of the area in feet, multiply those numbers together to get square feet, then multiply by the depth you want (in feet) and divide by 27. That gives you cubic yards. Most garden beds need 2 to 4 inches of mulch, which translates to roughly 1 cubic yard per 100 to 160 square feet.
The math is straightforward once you have your measurements. The hard part is measuring accurately and deciding how deep to go. This guide walks you through both.
Key Takeaways
- Measure your garden bed length and width in feet, multiply them together, then multiply by depth in feet and divide by 27 to get cubic yards.
- Most ornamental beds need 2 to 3 inches of mulch; vegetable gardens and newly planted areas often need 3 to 4 inches.
- Mulch settles over time, so add 10 to 15 percent extra to your calculation to account for settling in the first few months.
- If your bed is irregular or has curves, break it into rectangles, measure each one separately, then add the totals together.
- One cubic yard of mulch weighs 400 to 800 pounds depending on moisture content, so factor that into delivery if you are ordering in bulk.
Measure length and width in feet
Start with a measuring tape and measure the longest edge of your garden bed from end to end. Write this number down. Then measure the width—the distance from the front of the bed to the back. If your bed is rectangular, you now have what you need. If it is L-shaped, circular, or irregular, break it into rectangles and measure each one separately.
Measure in feet, not inches. If a bed is 10 feet 6 inches long, write it as 10.5 feet. If it is 10 feet 3 inches, that is 10.25 feet. This matters because the final number compounds through the calculation.
For curved beds, the easiest approach is to measure the longest straight line through the middle (the length) and the widest point across (the width), then treat it as a rectangle. You will overestimate slightly, but the difference is usually small enough that it does not matter in practice.
Decide on mulch depth and convert to feet
Mulch depth depends on what you are mulching and what you want it to do. Ornamental beds around shrubs and perennials typically need 2 to 3 inches to suppress weeds and retain moisture. Vegetable gardensPathways
Once you have chosen a depth in inches, convert it to feet by dividing by 12. Two inches is 0.17 feet. Three inches is 0.25 feet. Four inches is 0.33 feet. Write this number down—you will use it in the next step.
Keep in mind that mulch settles as it breaks down and as rain compacts it. After the first season, a 3-inch layer may compress to 2 inches. If you want consistent coverage year to year, add 10 to 15 percent extra to your order to account for settling.
Calculate cubic feet, then convert to cubic yards
Multiply length × width × depth (all in feet). This gives you cubic feet. For example, a bed that is 10 feet long, 4 feet wide, and 3 inches deep (0.25 feet) would be: 10 × 4 × 0.25 = 10 cubic feet.
Now convert cubic feet to cubic yards by dividing by 27 (because one cubic yard contains 27 cubic feet). In the example above: 10 ÷ 27 = 0.37 cubic yards. Most suppliers sell mulch in whole or half-yard increments, so you would round up to 0.5 cubic yards for a single bed, or combine it with other beds to reach a full yard.
If you have multiple beds, calculate each one separately, then add all the cubic yards together. This prevents rounding errors and gives you an accurate total for ordering.
Use a straightforward table for common bed sizes
| Bed Size (feet) | At 2 inches deep | At 3 inches deep | At 4 inches deep |
|---|---|---|---|
| 4 × 8 | 0.2 cubic yards | 0.3 cubic yards | 0.4 cubic yards |
| 5 × 10 | 0.3 cubic yards | 0.5 cubic yards | 0.6 cubic yards |
| 8 × 12 | 0.7 cubic yards | 1 cubic yard | 1.2 cubic yards |
| 10 × 15 | 1.1 cubic yards | 1.7 cubic yards | 2.2 cubic yards |
If your bed matches one of these sizes, you can read the yardage directly. If not, use the formula above. These numbers assume rectangular beds with straight edges.
Account for settling and order slightly more
Fresh mulch is fluffy and loose. Over the first few weeks and months, rain, foot traffic, and decomposition compress it. A 3-inch layer often settles to 2.5 inches by midsummer. To maintain consistent coverage, add 10 to 15 percent to your calculated total.
If your calculation shows you need 2 cubic yards, order 2.3 cubic yards instead. If you need 5 cubic yards, order 5.75 cubic yards. Most suppliers sell in half-yard increments, so round to the nearest half. This extra mulch also gives you material to top up beds in late summer or fall if settling is more pronounced than expected.
Understand mulch weight if ordering delivery
One cubic yard of mulch weighs between 400 and 800 pounds, depending on moisture content and mulch type. Freshly ground hardwood mulch with high moisture content can weigh 700 to 800 pounds per yard. Aged or dried mulch weighs closer to 400 to 500 pounds per yard. This matters if you are ordering delivery, because trucks have weight limits.
A standard pickup truck bed holds roughly 0.5 to 1 cubic yard of mulch, depending on how tightly it is packed. If you need more than 2 or 3 cubic yards, delivery from a landscape supplier is usually cheaper and easier than making multiple trips. Ask the supplier what their mulch weighs per yard when you order—they can tell you based on how recently it was ground and how much rain it has had.
Frequently Asked Questions
What if my garden bed is not a perfect rectangle?
Divide it into rectangles. Measure the length and width of each rectangle separately, calculate cubic yards for each, then add them together. For a circular bed, measure the diameter and treat it as a square—you will overestimate by about 20 percent, but that accounts for settling anyway.
Can I use this calculation for wood chips or bark instead of mulch?
Yes. The volume calculation is the same regardless of mulch type. The weight per cubic yard varies—bark is often lighter than hardwood mulch—so ask your supplier if weight matters for delivery.
How often do I need to remulch?
Most mulch breaks down and settles enough to need topping up every 1 to 2 years. In year one, add 1 to 2 inches of fresh mulch to maintain depth. After that, add 1 inch annually. You do not need to remove old mulch unless it has become compacted into a hard crust.
What if I measure in inches instead of feet?
Multiply length × width × depth (all in inches), then divide by 1,728 (the number of cubic inches in a cubic yard). This works but is more error-prone. Converting to feet first is simpler.
Should I measure mulch depth before or after spreading?
Measure the depth you want before ordering. Once mulch is spread, it settles unevenly—thicker in some spots, thinner in others. The depth you calculated is your target, not what you will see when ready after spreading.