Cubic Yard Calculator from Square Footage

This calculator converts an area in square feet and a depth in inches into a volume in cubic yards and cubic feet. Enter the length and width of the area in feet, the depth you want to fill in inches, and the tool returns the amount of material needed in cubic yards (the primary result) and cubic feet. This is the standard way to estimate how much soil, mulch, gravel, or concrete to order for a rectangular space.

Formula

The core relationship is simple: volume = area × depth. To get cubic yards from square feet, you multiply the area (length × width, in feet) by the depth (in feet) and then divide by 27, because one cubic yard equals 27 cubic feet. Since depth is often given in inches, you can combine the conversion into one step:

Volume (yd³) = (Length (ft) × Width (ft) × Depth (in)) / 324

The constant 324 comes from multiplying 27 (cubic feet per cubic yard) by 12 (inches per foot). Each variable is defined as:

• Length (l) – the longer side of the rectangular area, in feet.
• Width (w) – the shorter side of the rectangular area, in feet.
• Depth (d) – how deep you want the material, in inches.
• Volume (yd³) – the result, in cubic yards.

If you prefer to work in feet for depth, the formula becomes (l × w × d_ft) / 27. The calculator uses inches because that is how most people measure topsoil, mulch, or gravel depth.

Worked Example

Using the default values from the calculator: a lawn that is 40 feet long, 25 feet wide, and you want a 3-inch layer of soil.

1. Calculate the area: 40 ft × 25 ft = 1,000 square feet.
2. Convert the depth to feet: 3 in ÷ 12 = 0.25 ft.
3. Multiply area by depth: 1,000 sq ft × 0.25 ft = 250 cubic feet.
4. Divide by 27: 250 ÷ 27 = 9.259… cubic yards.

The calculator gives 9.26 yd³ (rounded to two decimals) and 250 ft³. That matches the formula directly: (40 × 25 × 3) / 324 = 3000 / 324 = 9.259. So you would order about 9.26 cubic yards, or more realistically 10 cubic yards, since suppliers usually sell in whole or half yards.

Why Convert Square Footage to Cubic Yards?

Square footage only describes a two-dimensional surface. When you need to buy materials that fill a space—like topsoil for a garden bed, mulch for landscaping, gravel for a path, or concrete for a slab—you are buying volume, not area. A cubic yard is the standard unit for bulk materials in the US. Knowing the volume tells you how many trucks or bags to order, how much it will weigh (roughly), and how many trips you will need.

For example, a 10×10 garden bed with 6 inches of soil needs 50 cubic feet, or about 1.85 cubic yards. Without the conversion, you might order too little and run short mid-project, or too much and have a pile of leftover material.

How to Use the Calculator Correctly

Follow these steps to get an accurate estimate:

• Measure the length and width of the area in feet. For irregular shapes, break them into rectangles and add the volumes together.
• Decide on the depth in inches. Common depths: 2–3 inches for mulch, 3–4 inches for topsoil over a lawn, 4–6 inches for a new garden bed, 6–8 inches for gravel under a patio.
• Enter the numbers and read the cubic yards result. Round up to the next half or whole yard when ordering.
• If the area is not a rectangle, calculate each rectangle separately and sum the cubic yards.

For circular areas, use the formula π × radius² × depth, then divide by 27. For triangular areas, use 0.5 × base × height × depth, then divide by 27.

Common Mistakes and How to Avoid Them

The most frequent error is mixing units. If you measure the area in feet but the depth in inches, you must convert first. The calculator does that for you, but if you do it by hand, remember to divide inches by 12 before multiplying.

Another mistake is ignoring the difference between cubic yards and square yards. A cubic yard is a volume, while a square yard is an area. They are not interchangeable. Also, be careful with depth: 3 inches is 0.25 feet, not 0.3 feet. Small errors in depth become large errors in volume when the area is big.

Finally, remember that the result is an estimate. Real-world surfaces are rarely perfectly flat, and materials settle. Adding 5–10% extra is standard practice for most projects.

Limitations of the Formula

This formula assumes a flat, uniform depth across a rectangular area. If your site has slopes, dips, or varying depths, the estimate will be off. For a sloped yard, you might need to measure at several points and average the depth. Also, the formula gives the theoretical volume of the space, not the actual volume of material delivered. Loose materials like mulch and soil compress when placed, so you may need more than the calculated amount. Conversely, if you are filling a hole, the material may settle and require a top-up.

For concrete, the volume is usually ordered in cubic yards, but ready-mix trucks have minimums and you pay for the whole yard even if you use less. Check with your supplier about how they handle partial yards.

Cost Considerations and Ordering

Once you have the cubic yards, you can estimate cost by multiplying by the price per cubic yard from your local supplier. Prices vary widely by material and region, so it is always best to call for a quote. Many suppliers sell in whole or half yards, so round up to the next half yard. For bagged material (like 2-cubic-foot bags of mulch), divide the cubic feet result by the bag size to get the number of bags. For example, 250 cubic feet ÷ 2 cu ft per bag = 125 bags. That is a lot of bags—bulk delivery is often cheaper for large projects.

Weight is another factor. A cubic yard of dry topsoil weighs roughly 2,000–2,500 pounds, while gravel can weigh up to 3,000 pounds per cubic yard. If you are hauling it yourself, check your vehicle’s payload capacity. For larger orders, delivery is usually the better option.

Frequently Asked Questions

How many square feet does a cubic yard cover at 3 inches deep?

One cubic yard equals 27 cubic feet. At a depth of 3 inches (0.25 feet), it covers 27 ÷ 0.25 = 108 square feet. At 2 inches deep, it covers 162 square feet; at 4 inches, it covers 81 square feet.

Can I use this calculator for any material?

Yes, the math is the same for any bulk material—soil, mulch, gravel, sand, or concrete. The only difference is the price per cubic yard and the weight, which you should check with your supplier.

What if my area is not a rectangle?

Break the area into rectangles, calculate the cubic yards for each, and add them together. For circles, use π × radius² × depth / 27. For triangles, use 0.5 × base × height × depth / 27.

Should I round up or down when ordering?

Always round up to the next half or full cubic yard. It is better to have a little extra than to run short mid-project. Most suppliers will not deliver a fraction of a yard, and leftover material can be used elsewhere.

How do I convert cubic yards back to square feet?

To get square footage, divide the cubic yards by the depth in feet (converted from inches). For example, 10 cubic yards at 3 inches (0.25 ft) covers 10 / 0.25 = 40 square yards, which is 360 square feet. Or use the formula: square feet = (cubic yards × 27) / depth in feet.

Related

• 1 Unit to Ton Calculator for Sand
• Retaining Wall Block Calculator: Blocks per Course
• Lawn Edging Calculator: Pieces and Stakes

in l | Lawn length | ft | 40 | 0 | 100000
in w | Lawn width | ft | 25 | 0 | 100000
in d | Depth | in | 3 | 0 | 120
out yd | Volume | yd³ | l * w * d / 324 | 2
out ft3 | Volume | ft³ | l * w * d / 12 | 1