Calculate soil volume by bed dimensions
The amount of soil you need depends on three measurements: the length, width, and depth of your raised bed. Multiply those three numbers together to get cubic feet, then convert to cubic yards if you're ordering in bulk. A bed that is 4 feet long, 2 feet wide, and 12 inches deep needs 8 cubic feet of soil—which is roughly 0.3 cubic yards.
Most raised beds are 6 to 12 inches deep. Shallower beds work for lettuce and herbs; deeper beds suit tomatoes, peppers, and root vegetables. If you're building a bed from scratch, 10 to 12 inches is a practical middle ground that handles most vegetables without excessive cost.
Use this formula: length (feet) × width (feet) × depth (feet) ÷ 27 = cubic yards. Soil is sold by the cubic yard at garden centers and landscape suppliers. One cubic yard fills roughly a 3-foot-by-3-foot-by-3-foot space and weighs between 1,200 and 1,500 pounds depending on moisture content.
Key Takeaways
- Multiply your bed's length, width, and depth in feet, then divide by 27 to find how many cubic yards you need.
- A standard 4-by-8-foot bed at 12 inches deep requires about 1 cubic yard of soil.
- Soil settles over time, so order 10 to 15 percent extra to top off after the first season.
- Bagged soil works for small beds under 4 cubic feet; bulk delivery is cheaper for anything larger.
- Garden soil, compost, and topsoil are not the same—most raised beds do best with a mix of all three rather than one type alone.
Common bed sizes and their soil needs
A 4-by-8-foot bed at 12 inches deep—the most common vegetable garden size—needs 1 cubic yard of soil. A 4-by-4-foot bed at the same depth needs 0.5 cubic yards. A 3-by-6-foot bed needs about 0.67 cubic yards. These are the sizes that fit standard landscape fabric and work well in most backyards.
Smaller decorative beds, like a 2-by-3-foot herb garden at 8 inches deep, need only about 0.15 cubic yards—roughly 4 bags of 40-pound bagged soil. Larger beds, like a 6-by-12-foot plot at 14 inches deep, need about 3 cubic yards. At that volume, bulk delivery from a landscape supplier is far cheaper than buying bags.
| Bed Size (length × width) | Depth | Cubic Feet | Cubic Yards | Approximate Bags (40 lb) |
|---|---|---|---|---|
| 2 × 3 feet | 8 inches | 4 | 0.15 | 4 |
| 3 × 6 feet | 10 inches | 15 | 0.56 | 14 |
| 4 × 4 feet | 12 inches | 16 | 0.59 | 15 |
| 4 × 8 feet | 12 inches | 32 | 1.19 | 30 |
| 6 × 12 feet | 14 inches | 84 | 3.11 | 78 |
Bagged soil versus bulk delivery
Bagged soil works well for beds under 0.5 cubic yards. A single 40-pound bag of garden soil covers about 0.3 cubic feet, so you'll need roughly 15 bags for a 4-by-4-foot bed at 12 inches deep. Bags are convenient if you have a truck or can carry them, and you can mix brands and types to get the blend you want.
Bulk soil delivered by truck is cheaper per cubic yard once you need more than 1 cubic yard. A landscape supplier will dump it in your driveway or yard for a flat delivery fee—usually $50 to $150 depending on distance. You then shovel it into the bed yourself. For a 4-by-8-foot bed, bulk is almost always the better deal.
Some suppliers offer a middle ground: they sell soil by the cubic yard but deliver it in bags stacked on a pallet. This costs more than loose bulk but less than buying individual bags at a garden center, and it saves you from shoveling.
Soil mix: garden soil, compost, and topsoil
Most raised beds perform best with a blend rather than a single soil type. Garden soil is topsoil mixed with organic matter and is the base layer. Compost adds nutrients and improves water retention—use 25 to 30 percent compost by volume. Topsoil alone is too dense and compacts over time; it's better as a filler or topping.
A practical mix is 60 percent garden soil, 30 percent compost, and 10 percent perlite or coarse sand for drainage. If you're ordering bulk, ask the supplier what they recommend for vegetable gardens in your region—they know the local soil and what works. If you're buying bags, you can layer them: garden soil on the bottom two-thirds, compost on top.
Avoid pure potting soil for raised beds—it's designed for containers and is too expensive for the volume you need. Avoid pure topsoil alone; it will compact and drain poorly. The blend matters more than the brand.
Account for settling and future refills
Soil settles as it absorbs water and as organic matter breaks down. Expect your bed to drop 1 to 2 inches in the first month and another inch or two over the first year. Order 10 to 15 percent extra soil to top off after the first season—this keeps your bed at working depth and replaces what has decomposed.
In subsequent years, add 1 to 2 inches of compost or aged manure each spring. This replaces organic matter and keeps the soil structure open. You won't need to refill the entire bed every year unless you're growing very heavy feeders like corn or squash year after year in the same space.
Where to order soil and what to ask
Local landscape suppliers, garden centers, and some hardware stores sell soil by the bag and bulk. Call ahead with your cubic yardage and ask what they have in stock—availability varies by season. In spring, popular blends sell out quickly. In fall, selection is usually better and prices may be lower.
Ask the supplier whether their soil is screened (free of rocks and debris), whether it contains weed seeds, and whether it's been tested for contaminants. Screened soil costs a bit more but saves you hours of picking through rocks. Ask about delivery fees and whether they can dump the soil close to where you'll use it—the closer, the less shoveling.
If you're ordering from a big-box store, check the bag weight and coverage claim on the label. A 40-pound bag typically covers 0.3 cubic feet, but some brands vary. Calculate backward from your total cubic feet needed to confirm the bag count.
Frequently Asked Questions
Can I use less soil if I put cardboard or landscape fabric on the bottom?
Cardboard or fabric on the bottom does not reduce the soil you need—it just prevents weeds from growing up from below. You still need the full depth of soil for roots to grow. The cardboard will decompose over one to two seasons and add organic matter as it breaks down.
What if I fill my bed with less soil than calculated and add more later?
You can, but it's less efficient. Soil settles unevenly if you add it in layers, and you'll spend more on multiple small deliveries. It's better to calculate once, order the full amount, and top off with compost in future years.
Do I need to buy new soil every year?
No. Add 1 to 2 inches of compost or aged manure each spring to replenish nutrients and organic matter. You only need to replace the entire bed if it becomes compacted, contaminated, or depleted after many years of heavy use—usually five years or more.
Is bagged compost the same as bagged garden soil?
No. Compost is decomposed organic matter and is nutrient-rich but loose and drains quickly. Garden soil is topsoil blended with compost and holds moisture better. Use compost as a topping or amendment, not as your entire bed fill.
What if my raised bed is an odd shape—not a rectangle?
Measure the area in square feet, multiply by depth in feet, then divide by 27 for cubic yards. For a circular bed 4 feet across and 12 inches deep, the area is about 12.5 square feet; multiply by 1 foot depth to get 12.5 cubic feet, or 0.46 cubic yards. Landscape suppliers can help you estimate for irregular shapes if you describe the dimensions.