Calculate soil volume by bed dimensions
The amount of dirt 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 are buying in bulk. A bed that is 4 feet long, 2 feet wide, and 12 inches deep holds 8 cubic feet of soil, which is roughly 0.3 cubic yards.
Most garden soil is sold by the cubic yard, and a single cubic yard fills a bed that is 4 feet by 8 feet by 4 inches deep, or 4 feet by 4 feet by 12 inches deep. Bagged soil is sold by the cubic foot or in smaller volumes like 2 cubic feet per bag. If your bed is small or you are filling multiple beds, bags may cost less per unit than bulk delivery, but bulk is cheaper for larger projects.
Depth matters more than most people expect. A 6-inch depth works for shallow-rooted crops like lettuce and herbs. Tomatoes, peppers, and root vegetables need 12 inches minimum. Potatoes and deep-rooted perennials like asparagus need 18 inches or more. If you are building a bed on top of existing grass or weeds, add 2 to 4 inches extra to account for settling and decomposition of the material underneath.
Key Takeaways
- Multiply length × width × depth in feet to find cubic feet, then divide by 27 to convert to cubic yards.
- Most vegetables need 12 inches of depth; shallow crops like lettuce need 6 inches, and root crops need 18 inches or more.
- Bulk soil is cheaper per cubic yard for beds larger than 4 feet by 8 feet, but bags are often more practical for small or oddly shaped beds.
- Add 2 to 4 extra inches of soil if your bed sits directly on grass or compacted ground, because the base layer will settle and break down.
Bagged soil versus bulk delivery
Bagged soil costs more per cubic foot but requires no delivery fee and no minimum order. A standard 2-cubic-foot bag costs between $3 and $8 depending on the brand and soil type. For a 4-by-8-foot bed at 12 inches deep, you would need 32 bags. That adds up quickly, but it works if you are filling one or two small beds or if you do not have space for a bulk delivery truck.
Bulk soil is delivered by the cubic yard and usually costs $30 to $60 per yard depending on your region and soil quality. A delivery fee of $50 to $100 is common. The math favors bulk when you need more than 10 to 12 cubic feet — roughly 5 to 6 standard bags. Many landscape suppliers will quote you over the phone if you give them your bed dimensions.
Soil quality varies widely between brands and suppliers. Garden soil, topsoil, and potting mix are different products. Garden soil is the cheapest and works for most raised beds; it is usually a mix of topsoil and compost. Topsoil alone is often too dense and compacts over time. Potting mix is expensive and unnecessary for raised beds — it is designed for containers. Ask the supplier what is in the soil before you order, or read the bag label if you are buying bagged soil.
Account for settling and amendments
Soil settles after the first watering and continues to settle slightly over the first season. If you fill your bed to the very top, you will see a 1 to 2 inch gap within a week. Fill to within 2 inches of the rim to leave room for settling and mulch.
Many gardeners mix amendments into the soil rather than using straight garden soil. Adding 20 to 30 percent compost by volume improves drainage and adds nutrients. If you are mixing, calculate the total volume you need, then order 70 to 80 percent garden soil and 20 to 30 percent compost. A cubic yard of compost weighs more than a cubic yard of soil, so if you are buying in bulk, ask the supplier to deliver both materials at once.
If your bed is sitting on clay or compacted ground, consider laying down cardboard or landscape fabric first to block weeds and slow water drainage. This does not change how much soil you need, but it does affect how well your plants will grow.
Common bed sizes and soil volumes
| Bed dimensions (L × W × D) | Cubic feet | Cubic yards | Approximate bags (2 cu ft each) |
|---|---|---|---|
| 4 ft × 2 ft × 6 in | 4 | 0.15 | 2 |
| 4 ft × 2 ft × 12 in | 8 | 0.3 | 4 |
| 4 ft × 4 ft × 12 in | 16 | 0.6 | 8 |
| 4 ft × 8 ft × 12 in | 32 | 1.2 | 16 |
| 6 ft × 3 ft × 18 in | 27 | 1 | 14 |
Ordering tips to avoid waste
Measure your bed twice before you order. A mistake of even 6 inches in one dimension changes the volume by 10 to 20 percent. If your bed is not a perfect rectangle, break it into rectangles, calculate each section, and add them together.
Order slightly more than your calculation suggests — 5 to 10 percent extra — because soil settles and you may need to top off the bed after the first season. It is easier to use leftover soil in containers or garden borders than to order a second delivery.
If you are buying bags, check the weight limit on your vehicle and the weight of the bags. A 2-cubic-foot bag of soil weighs 40 to 50 pounds. Sixteen bags for a standard 4-by-8 bed weigh 640 to 800 pounds, which exceeds the payload of many cars and light trucks. Plan multiple trips or arrange delivery if you are buying that much bagged soil.
Frequently Asked Questions
Can I use topsoil straight from my yard instead of buying soil?
Yes, if it is not compacted and does not contain clay, rocks, or weed seeds. Yard soil often needs amendment with compost to improve structure and drainage. If you dig from your yard, screen it through a 1/2-inch mesh to remove rocks and roots, then mix in 20 to 30 percent compost before filling the bed.
Do I need to fill the entire depth with soil, or can I use gravel or wood chips at the bottom?
You can layer materials to save soil cost, but the top 8 to 12 inches must be actual soil or compost for roots to grow. Wood chips at the bottom decompose over time and create air pockets that improve drainage. Gravel does not decompose and can trap water. If you layer, still calculate your soil volume for the top portion only.
How much does a cubic yard of soil weigh?
Garden soil weighs 1,200 to 1,400 pounds per cubic yard when dry, and 1,500 to 1,800 pounds when wet. Compost is lighter, around 800 to 1,000 pounds per cubic yard. Weight matters if you are loading bags into a vehicle or if your raised bed is on a deck or roof.
What if I order too much soil?
Use it to top off the bed after settling, fill containers, amend existing garden beds, or create a small berm for drainage. Bagged soil keeps for years if stored in a dry place. Bulk soil left in a pile will compact and may develop weeds, so use it within a few weeks or spread it thin across your yard.
Should I buy premium garden soil or the cheapest option?
Mid-range garden soil works fine for most vegetables. Cheap soil is often mostly clay or sand with little compost. Premium soil costs more but usually contains more compost and fewer rocks. For a first bed, buy mid-range soil and mix in your own compost rather than paying for premium blends.