A yard of mulch is 27 cubic feet, and you measure it by multiplying the length, width, and depth of the area you want to cover

One cubic yard equals 27 cubic feet. To find out how many yards you need, measure your garden bed in feet, then multiply length × width × depth (in feet), and divide by 27. The depth matters most—most landscapers spread mulch 2 to 4 inches deep, and that depth choice changes how many yards the same bed will need.

The math is straightforward once you have three measurements. A 10-foot-long bed that is 3 feet wide and 3 inches deep, for example, needs (10 × 3 × 0.25) ÷ 27 = 0.28 cubic yards, or roughly one-third of a yard. A larger bed 20 feet long, 4 feet wide, and 3 inches deep needs (20 × 4 × 0.25) ÷ 27 = 0.74 cubic yards, close to three-quarters of a yard.

Key Takeaways

  • Measure your bed's length and width in feet, then decide on a depth between 2 and 4 inches (convert inches to feet by dividing by 12).
  • Multiply length × width × depth in feet, then divide the result by 27 to get cubic yards.
  • Mulch settles over time, so ordering 10 to 15 percent extra accounts for settling and future top-ups.
  • Irregular or curved beds can be broken into rectangles and measured separately, then added together.
  • Depth affects both the look and the function—shallower mulch (2 inches) works for maintenance, while deeper mulch (3 to 4 inches) suppresses weeds better.

Converting inches to feet for the depth measurement

Depth is almost always given in inches, but the formula works in feet, so you must convert. Divide the number of inches by 12. A 2-inch depth becomes 2 ÷ 12 = 0.17 feet. A 3-inch depth becomes 3 ÷ 12 = 0.25 feet. A 4-inch depth becomes 4 ÷ 12 = 0.33 feet.

This conversion is where most people make mistakes. If you forget to convert and use 3 instead of 0.25, your answer will be 12 times too large, and you will order far more mulch than you need. Write down the converted number before you multiply.

Measuring rectangular and square beds

For a straightforward rectangle, measure the length and width at ground level with a tape measure. If the bed is not a perfect rectangle, measure the longest length and the widest width, and use those numbers—you will have a small amount of extra mulch, which is normal.

Measure in feet and inches, then convert everything to feet as a decimal. A bed that is 12 feet 6 inches long is 12.5 feet. A bed that is 8 feet 3 inches wide is 8.25 feet. Once all three measurements (length, width, and depth) are in feet as decimals, multiply them together and divide by 27.

Breaking irregular beds into sections

If your bed is L-shaped, curved, or has an odd outline, divide it mentally into rectangles. Measure each rectangle separately, calculate the cubic yards for each one, then add them together.

For example, an L-shaped bed might be one 10-foot by 3-foot rectangle plus one 6-foot by 2-foot rectangle. Calculate (10 × 3 × 0.25) ÷ 27 for the first section and (6 × 2 × 0.25) ÷ 27 for the second, then add the results. This method works for any shape as long as you can break it into rectangles.

Why depth matters for mulch coverage

A 2-inch depth is the minimum for mulch to do its job—it suppresses some weeds and retains some moisture. Most landscapers use 3 inches as the standard, which gives better weed control and moisture retention without looking excessive. A 4-inch depth is common in high-traffic areas or where you want maximum weed suppression, but it can look heavy in a small bed.

Mulch settles as it breaks down and as rain compacts it, so the depth you lay down will be slightly deeper than the depth that remains after a few months. Many homeowners add a top-up layer of 1 to 2 inches each spring to maintain the original depth. Plan for this by ordering 10 to 15 percent extra mulch when you first buy.

Accounting for settling and future maintenance

When you receive a delivery of mulch, it will settle during transport and spread. The pile will look smaller once it is spread across your bed than it did in the truck. This is normal and does not mean you received less than you ordered—the mulch is the same volume, just distributed.

To avoid running short, add 10 to 15 percent to your calculated amount. If your math says you need 5 cubic yards, order 5.5 to 5.75 cubic yards. The extra will give you a buffer for settling, for areas you may have underestimated, and for a spring top-up layer later.

Using an online calculator as a double-check

Once you have your three measurements in feet, you can plug them into a free online mulch calculator to verify your math. Search "cubic yard calculator" and enter length, width, and depth. The calculator will show you the result in cubic yards. This takes 30 seconds and catches arithmetic errors before you place an order.

Some landscape supply companies also have calculators on their websites. These are useful because they sometimes let you enter measurements in feet and inches separately, so you do not have to convert to decimals yourself. The result is the same either way.

Frequently Asked Questions

What if my bed is circular or has a curved edge?

Measure the longest distance across the circle (the diameter) and divide it by 2 to get the radius. Then use the formula (radius × radius × 3.14 × depth) ÷ 27. For a curved edge, measure the bed as if it were a rectangle that encloses the curve, calculate that, and you will have a slight overage—which is fine for mulch.

Should I measure before or after removing old mulch?

Measure the bare soil after you have removed the old mulch. This gives you the true dimensions of the bed and ensures your new mulch sits at the right depth on fresh ground. If you measure over old mulch, your depth calculation will be off.

How much does a cubic yard of mulch weigh?

A cubic yard of mulch typically weighs 400 to 800 pounds depending on the type and moisture content. Hardwood mulch is heavier than pine, and wet mulch weighs more than dry. If you are ordering delivery, the weight matters for truck capacity, but most suppliers account for this when they quote you.

Can I order mulch in bags instead of by the yard?

Yes. A standard bag of mulch is usually 2 or 3 cubic feet. Divide your total cubic feet (length × width × depth in feet) by 2 or 3 to find how many bags you need. Bags cost more per cubic foot than bulk delivery, but they work well for small beds or if you do not have space for a truck delivery.

What if I want a different depth in different parts of the bed?

Measure and calculate each section separately with its own depth, then add the cubic yards together. For example, if half your bed gets 2 inches and half gets 4 inches, calculate each half with its own depth and add the results. This is common when you want deeper mulch around trees and shallower mulch in open areas.