Dirt Calculator: Square Feet & Cubic Yards

This dirt calculator tells you how much soil, topsoil, or fill dirt you need in cubic feet and cubic yards, based on the square footage of the area you want to cover and how deep you want the layer to be. You enter the area’s length and width in feet (or the total square feet directly) and the desired depth in inches; the calculator returns the volume in cubic feet and cubic yards, plus the estimated weight in tons. It is designed for garden beds, raised planters, lawn leveling, and small construction fills.

Formula

The core formula is straightforward: volume = length × width × depth. Since depth is usually given in inches and length/width in feet, convert depth to feet first by dividing by 12. The result is cubic feet. To get cubic yards, divide by 27 (because 1 cubic yard = 27 cubic feet).

• Volume (ft³) = L (ft) × W (ft) × D (in) ÷ 12
• Volume (yd³) = Volume (ft³) ÷ 27
• Weight (tons) = Volume (ft³) × 0.05 (approximate for dry topsoil)

Variables: L = length in feet, W = width in feet, D = depth in inches. The weight factor of 0.05 tons per cubic foot (about 100 lb/ft³) is a common average for dry, loose topsoil. Wet soil or dense fill can weigh more, up to 0.06–0.07 tons/ft³.

Worked Example

Using the default values: length = 10 ft, width = 5 ft, depth = 6 in.

1. Convert depth to feet: 6 in ÷ 12 = 0.5 ft
2. Calculate cubic feet: 10 × 5 × 0.5 = 25 ft³
3. Convert to cubic yards: 25 ÷ 27 = 0.926 yd³
4. Estimate weight: 25 × 0.05 = 1.25 tons

So for a 10×5 ft bed at 6 inches deep, you need 25 cubic feet (about 0.93 cubic yards) of dirt, weighing roughly 1.25 tons. The calculator rounds to 25.0 ft³, 0.93 yd³, and 1.25 tons.

Why Square Footage Matters

Most soil and mulch is sold by volume (cubic feet or cubic yards), not by area. Knowing the square footage alone isn’t enough – you also need the depth. For example, a 100 ft² garden bed at 2 inches deep needs only 16.7 ft³, but the same bed at 12 inches deep needs 100 ft³. This calculator combines your square footage with depth to give the volume you actually need to order.

Common depth guidelines: for new garden beds, 6–8 inches of topsoil is typical; for raised beds, 12–18 inches; for lawn topdressing, 1/4 to 1/2 inch. Always check with your supplier for their recommended depth for your specific project.

How to Use the Calculator

Enter the length and width of the area in feet. If your area is irregular, break it into rectangles, calculate each, and add the volumes together. Then enter the depth in inches. The calculator gives you three numbers:

• Cubic feet – useful for bagged soil (usually sold in 1–3 ft³ bags).
• Cubic yards – the standard unit for bulk deliveries (truckloads).
• Estimated tons – helps when ordering by weight, especially for fill dirt.

For example, a 20×10 ft patio base at 4 inches deep: 20 × 10 × (4/12) = 66.7 ft³ = 2.47 yd³. You’d order about 2.5 cubic yards of crushed stone or fill.

Common Mistakes and Misconceptions

A frequent error is mixing units – using inches for length and feet for depth without converting. Always convert everything to feet before multiplying. Another mistake is forgetting that the depth is in inches, not feet, leading to a 12× overestimate.

Many people confuse cubic feet with square feet. Square feet is area (length × width), while cubic feet is volume (area × depth). This calculator needs both area and depth to give a volume. Also, soil settles after watering, so it’s wise to order 10–15% extra to account for compaction.

Weight estimates vary widely: dry topsoil ~0.05 tons/ft³, moist topsoil ~0.06 tons/ft³, and wet clay can be ~0.07 tons/ft³. The calculator uses 0.05 as a conservative average; check with your supplier for exact density.

How to Choose the Right Dirt

Not all dirt is the same. The calculator gives volume, but the type of material matters for your project:

• Topsoil – for gardens and lawns; contains organic matter.
• Fill dirt – for leveling or backfilling; usually subsoil with less organic matter.
• Compost – for amending soil; lighter and more expensive.
• Sand or gravel – for drainage or base layers; different density.

For raised beds, a mix of topsoil and compost is common. For leveling a yard, fill dirt is cheaper. Always ask your supplier about the material’s compaction rate – some shrink more than others.

Cost and Ordering Considerations

While this calculator doesn’t provide prices (they vary by region and supplier), knowing your cubic yards helps you compare quotes. Bulk soil is usually cheaper per yard than bagged, but requires delivery. For small projects (under 1 yd³), bags may be more practical. A typical pickup truck holds about 2–3 cubic yards, but check your truck’s capacity – weight limits often hit before volume limits.

When ordering, mention the volume in cubic yards and ask about delivery fees. Some suppliers require a minimum order (e.g., 5 yd³). Also, consider that wet soil weighs more, so a truck may carry less volume if the material is damp.

Safety and Practical Tips

Handling large amounts of dirt can be physically demanding. Use proper lifting techniques (bend knees, not back) when moving bags or wheelbarrows. For deliveries, keep children and pets away from the drop zone. If you’re building a raised bed over a lawn, consider removing grass first to prevent weeds.

For deep fills (over 12 inches), check for buried utilities before digging. Also, ensure proper drainage – soil that’s too compacted can cause water pooling. Always wear gloves and a dust mask when working with dry soil, as it may contain dust or mold.

Frequently Asked Questions

How many cubic feet are in a cubic yard?

There are 27 cubic feet in one cubic yard (3 ft × 3 ft × 3 ft = 27 ft³). This is why the calculator divides cubic feet by 27 to get cubic yards.

How many bags of soil do I need?

Divide the total cubic feet by the bag size. For example, if you need 25 ft³ and buy 2 ft³ bags, you need 13 bags (25 ÷ 2 = 12.5, round up to 13). Always round up to cover spillage and settling.

How deep should I make a raised garden bed?

For most vegetables, 12 inches is sufficient, but 18 inches is better for root crops like carrots or potatoes. For shallow-rooted plants like lettuce, 6 inches can work. This calculator can help you determine the volume needed for any depth.

What is the difference between topsoil and fill dirt?

Topsoil is the upper layer of soil, rich in organic matter and nutrients, suitable for growing plants. Fill dirt is subsoil, lower in organic matter, used for filling holes or leveling ground. Fill dirt is usually cheaper and more compact.

How much does a cubic yard of dirt weigh?

Dry topsoil weighs about 2,700 pounds (1.35 tons) per cubic yard. Wet soil can weigh up to 3,500 pounds (1.75 tons) per cubic yard. The calculator uses an average of 2,700 lb/yd³ (0.05 tons/ft³).

How do I measure an irregular area?

Break the area into rectangles, calculate the volume for each, and add them together. For a circular bed, use the formula π × radius² × depth. For a triangular area, use 0.5 × base × height × depth. Then sum all volumes.

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in l | Length | ft | 10 | 0
in w | Width | ft | 5 | 0
in d | Depth | in | 6 | 0
out cubic_ft | Cubic feet | ft³ | l * w * (d / 12) | 1
out cubic_yd | Cubic yards | yd³ | (l * w * (d / 12)) / 27 | 2
out tons | Estimated tons | tons | (l * w * (d / 12)) * 0.05 | 2