Soil Calculator — Free Soil Volume & Topsoil Estimator
Calculate the exact soil volume in cubic feet and cubic yards, total bags by size, waste allowance, and cost for raised beds, garden beds, and topsoil delivery.
Estimate soil volume for raised beds, garden beds & topsoil.
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How to Use the Soil Calculator — Step by Step
- Choose a shape. Pick Rectangle for square or rectangular beds, Circle for round beds, or Area (sq ft) if you already know the footprint of an irregular space and just want to type it in directly.
- Enter the dimensions. Type the length and width in feet (or the radius / total area for the other shapes). Decimal values such as 4.5 are fine.
- Set the depth in inches. Most raised beds are filled to 12 inches. Use 6 inches for shallow annual beds and 18–24 inches for deep-rooted crops like carrots and potatoes.
- Pick a buying method. Choose Bags for small jobs or Bulk (cubic yards) when ordering a truckload. Bulk almost always costs less per cubic yard, but check delivery fees.
- Adjust waste and extra soil. The default of 10% covers spillage, compaction after watering, and the natural settling that happens in the first few weeks.
- Add a price (optional). Enter a price per bag or per cubic yard to see an estimated total cost. Leave it blank to skip the cost estimate.
- Read your results. The summary lists your area, the total volume in cubic feet and cubic yards, the volume including waste, and exactly how many bags or cubic yards to order.
The math behind it is simple: volume (cubic feet) equals area (square feet) times depth (feet). A 4×4 ft raised bed filled 12 inches deep holds 16 cubic feet of soil — about 0.59 cubic yards, or 0.65 cubic yards once you add 10% for waste and settling. That works out to 18 standard 1-cubic-foot bags. For larger projects, divide cubic feet by 27 to get cubic yards, then compare prices against bags. One cubic yard covers roughly 54 square feet at 6 inches deep, or 27 square feet at 12 inches.
Soil Types
Not all soil is the same, and choosing the right type matters as much as getting the volume right. Here is how the four most common options compare.
| Soil Type | Best For | Key Facts |
|---|---|---|
| Topsoil | Leveling lawns, filling low spots, underlayment for beds | General-purpose and affordable; low in organic matter, often screened |
| Garden Soil | Raised beds, flower beds, vegetable beds | Enriched with compost and nutrients; better structure and water retention |
| Potting Mix | Containers, pots, hanging baskets | Soilless and lightweight; drains fast, dries quickly in open beds, costly by volume |
| Compost | Amending existing soil, side-dressing plants | Rich, dark organic matter; improves drainage, aeration and fertility |
For raised vegetable beds, most gardeners blend garden soil with compost in a ratio between 70:30 and 50:50. Pure topsoil is fine for leveling and lawns, but it is low in organic matter for food crops. Potting mix is engineered for the confined space of a pot and dries out far too quickly in large open beds, so reserve it for containers.
How to Measure Your Garden Beds
Measuring your bed correctly is half the job. Follow these simple rules, then feed the numbers into the calculator.
- Rectangular beds: measure the inside length and inside width in feet and multiply them. Ignore the thickness of the timber walls.
- Circular beds: measure the diameter across the center, then use the formula area = 3.14 × radius². For a 6-foot-wide bed, that is 3.14 × 3² ≈ 28.3 square feet.
- Irregular or L-shaped beds: split the footprint into rectangles and circles, calculate each area, and add them together. If you already know the total square footage, just pick the Area (sq ft) shape in the calculator.
- Depth: measure the planned depth in inches, not the full height of the frame. If you intend to fill a 12-inch frame only 10 inches full, enter 10.
- Convert units carefully: divide inches by 12 to get feet, and remember that 1 cubic yard = 27 cubic feet.
When in doubt, over-estimate the depth slightly rather than the area. An extra inch of depth in a large bed can mean several extra bags, while an area you measured slightly short is far more annoying to fix mid-project.
Sample Calculations
The table below shows typical results for common bed sizes. All figures include 10% extra for waste and settling, and bag counts assume standard 1-cubic-foot bags.
| Bed | Size (ft) | Depth (in) | Area (sq ft) | Volume (cu ft) | Volume (yd³) | Incl. waste (yd³) | Bags needed |
|---|---|---|---|---|---|---|---|
| Raised bed | 4 × 4 | 12 | 16 | 16 | 0.59 | 0.65 | 18 |
| Raised bed | 8 × 4 | 12 | 32 | 32 | 1.19 | 1.30 | 36 |
| Circular bed | r = 3 | 12 | 28.3 | 28.3 | 1.05 | 1.15 | 32 |
| Garden bed | 10 × 10 | 6 | 100 | 50 | 1.85 | 2.04 | 55 |
| Garden bed | 12 × 12 | 6 | 144 | 72 | 2.67 | 2.93 | 80 |
| Backyard bed | 20 × 10 | 8 | 200 | 133.3 | 4.94 | 5.43 | 147 |
Notice how the numbers scale: doubling the depth doubles the volume, and bag counts jump quickly for large areas. That is why buying in bulk starts to make sense around the one-cubic-yard mark — 27 bags of 1 cubic foot equal a single cubic yard, and bulk deliveries usually beat bag prices by a wide margin.
Tips to Save on Soil
- Buy in bulk for anything bigger than a small raised bed. Bags typically cost three to six times more per cubic foot than bulk soil.
- Compare price per cubic foot, not per bag when shopping bags of different sizes.
- Stretch your soil with compost or existing garden dirt where the mix allows, especially at the bottom of deep beds.
- Factor in delivery. A cheap bulk price can disappear under a hefty delivery fee, so always ask for a delivered quote.
- Time your purchase. Landscape suppliers often run sales in early spring and fall when projects peak.
- Order 5–10% extra, not more. Soil settles naturally, but unused bags are hard to store and surplus bulk soil cannot be returned.
Keep the project moving with our other free tools: estimate a fresh layer of ground cover with the Mulch Calculator, plan paths and drainage with the Gravel Calculator, or work out flooring and tiling areas with the Tile Calculator.
For a deeper look at what topsoil is, how it forms, and how it differs from subsoil, see this overview of topsoil on Wikipedia.