Cubic Feet to Cubic Yards: The Conversion, a Chart and Common Mistakes

Bagged soil and mulch are labelled in cubic feet. Bulk material, concrete and fill dirt are sold in cubic yards. Switching between the two is something every gardener and DIYer ends up doing, and it is where many estimates go wrong. The conversion itself is simple; the mistakes come from the steps around it.

The conversion

cubic yards = cubic feet ÷ 27
cubic feet = cubic yards × 27

The 27 is not arbitrary. A yard is 3 feet, and volume has three dimensions, so a cubic yard is 3 × 3 × 3 = 27 cubic feet. The same logic gives 1,728 cubic inches in a cubic foot (12 × 12 × 12) and 46,656 cubic inches in a cubic yard (36 × 36 × 36).

Quick conversion chart

Cubic feet	Cubic yards	Cubic yards	Cubic feet
10	0.37	0.25	6.75
20	0.74	0.5	13.5
27	1.00	1	27
50	1.85	2	54
100	3.70	3	81
200	7.41	5	135
500	18.52	10	270

From bags to yards

Bag sizes vary, so convert through cubic feet. A yard is 27 cubic feet, which means:

• 1.5 cu ft bags: 18 bags per yard
• 2 cu ft bags: 13.5 bags per yard
• 3 cu ft bags: 9 bags per yard

If a store sells 2 cubic-foot bags of mulch at $4.50, a yard's worth costs 13.5 × $4.50 = $60.75. Compare that with the bulk price plus delivery to see which wins for your quantity.

Mistake 1: mixing inches and feet

This is the most common error by far. If a bed is 10 ft by 8 ft and you want 3 inches of mulch, multiplying 10 × 8 × 3 gives 240, which looks like cubic feet but is really "square feet times inches." The depth must be in feet: 3 inches is 0.25 ft, so the true volume is 10 × 8 × 0.25 = 20 cubic feet, or 0.74 yards. The wrong method would have you ordering twelve times too much.

A quick way to avoid it: divide the depth in inches by 12 before you multiply, or use a tool like the cubic yard calculator that lets you choose a unit for each dimension.

Mistake 2: confusing square feet with cubic feet

Square feet measure flat area; cubic feet measure volume. A product that "covers 12 square feet at 2 inches" is describing 2 cubic feet. When you have only an area, you cannot get a volume without a depth. Measure the area first with the square footage calculator, then add the depth.

Mistake 3: dividing by 9 instead of 27

Nine is the number of square feet in a square yard. People who remember "divide by 9" from flooring or carpet estimates sometimes apply it to volume. Dividing cubic feet by 9 overstates your need by a factor of three.

Mistake 4: forgetting compaction

The math gives the volume of the finished, settled layer. Loose material delivered by truck takes up more space than it will once raked, watered and walked on. Allow roughly 5–10% extra for mulch and gravel. Soil used to fill a low spot can settle considerably more, so many landscapers add 15–20% and top up later if needed.

Worked example: a raised bed

A raised bed is 8 ft long, 4 ft wide and 18 inches deep. Depth in feet is 18 ÷ 12 = 1.5. Volume is 8 × 4 × 1.5 = 48 cubic feet. In yards that is 48 ÷ 27 = 1.78. Adding 15% because new soil settles gives 2.04 yards, so two yards will fill it with a little mounding on top. In 1.5 cu ft bags of raised-bed mix you would need 48 ÷ 1.5 = 32 bags before settling allowance, which shows why bulk usually wins for anything larger than a single small bed.

Metric conversions

One cubic meter equals 1.308 cubic yards, and one cubic yard equals 0.7646 cubic meters. If a plan is in metric, calculate cubic meters and multiply by 1.308 for a US supplier. One cubic foot is 0.0283 cubic meters, or about 28.3 liters, which is handy when bag labels list liters.

Summary

• Divide cubic feet by 27 to get cubic yards; multiply yards by 27 to get feet.
• Convert every measurement to feet before multiplying.
• Use 9 only for square yards, never for cubic yards.
• Add an allowance for settling and round up to what your supplier sells.