Calculate Your Raised Bed Soil Volume

An 8-by-4-by-2 raised bed holds 64 cubic feet of soil. To find this, multiply length × width × depth: 8 × 4 × 2 = 64. Since soil is sold by the cubic yard, divide 64 by 27 (the number of cubic feet in one cubic yard) to get 2.37 cubic yards. Round up to 2.5 cubic yards to account for settling and to fill the bed completely to the rim.

If your supplier measures in bags instead of bulk, a standard 2-cubic-foot bag of potting soil or garden soil means you'll need 32 bags to fill the bed exactly. Most gardeners buy 35 to 40 bags to may support they have enough after the soil compacts in the first week.

The math changes slightly if your bed's measurements are in different units. If you measured in inches (96 inches long, 48 inches wide, 24 inches deep), convert to feet first by dividing by 12, then multiply. This gives you the same 64 cubic feet.

Key Takeaways

  • An 8×4×2 bed requires 2.5 cubic yards of soil, or about 35 to 40 standard 2-cubic-foot bags.
  • Soil settles after the first watering, so buying slightly more than the calculated amount prevents an underfilled bed.
  • Bulk soil from a landscape supplier is usually cheaper per cubic yard than bagged soil, but requires delivery or pickup.
  • The type of soil you choose—garden soil, potting mix, or a blend—affects both cost and drainage, so compare prices before ordering.

Bulk Soil vs. Bagged Soil: Cost and Convenience

Bulk soil from a landscape supply yard typically costs $25 to $50 per cubic yard, making 2.5 cubic yards run $60 to $125 before delivery. Many suppliers charge $50 to $100 for delivery depending on distance. Bagged soil at a garden center costs $3 to $8 per 2-cubic-foot bag, so 35 bags runs $105 to $280 with no delivery fee if you can carry them home.

Bulk soil makes sense if you have a truck or trailer, or if the supplier delivers to your area cheaply. Bagged soil works better if you're filling one bed, live in an apartment, or want to avoid a delivery charge. Some garden centers will load bags into your vehicle if you buy enough, which saves a trip.

Check whether the bulk soil is screened (finer, better for vegetables) or unscreened (coarser, cheaper). Bagged potting mix is usually finer and lighter than bagged garden soil, so it drains faster but costs more.

Soil Settling and Why You Need Extra

New soil compacts by 10 to 20 percent in the first two weeks as it absorbs water and the particles shift. A bed filled exactly to the rim will drop noticeably after the first watering. Buying 2.5 to 3 cubic yards instead of exactly 2.37 gives you a buffer so the bed stays full enough to plant without gaps.

If you fill the bed and then water it, you'll see the soil level drop within hours. Wait a day, then add more soil to bring it back to the rim before planting. This second filling is why many gardeners keep a few extra bags on hand or ask the supplier to deliver a little extra.

Measuring Your Bed Correctly

Before you order, measure the interior dimensions of your bed, not the outside. If your bed is made from 2-by-10 boards, the inside length and width are about 1.5 inches shorter on each side than the outside measurement. Measure from the inside bottom corner to the opposite inside bottom corner for length and width, and from the inside bottom to the inside top for depth.

If your bed is not a perfect rectangle—for example, if one corner sags or the boards bow—measure the length and width at the top and bottom, then use the average. For depth, measure at all four corners and use the average. This prevents ordering too little or too much.

Write down your measurements in feet and decimals (8.5 feet, not 8 feet 6 inches) before you call the supplier. This makes the conversation faster and reduces the chance of a mistake.

Soil Mixes for Different Plants

A garden soil blend—usually topsoil mixed with compost—works well for vegetables and herbs and costs less than potting mix. It drains reasonably well and holds nutrients. A potting mix (also called potting soil) is lighter, drains faster, and is better for shallow-rooted plants like lettuce or for beds in areas with heavy rain, but costs more per cubic yard.

Many gardeners split the difference by filling the bottom third with cheaper garden soil and the top two-thirds with potting mix or compost. This saves money while keeping the root zone light and well-draining. If you do this with an 8×4×2 bed, you'd use about 1 cubic yard of garden soil and 1.5 cubic yards of potting mix.

Ask the supplier what's in their "garden soil" or "potting mix"—some are mostly compost, others are mostly topsoil. The label should list the contents. Avoid anything labeled "fill dirt" or "construction soil," which is too dense for vegetables.

Ordering and Delivery Tips

Call the supplier at least a day or two before you need the soil, especially if you want delivery. Have your measurements and bed type ready (wood, composite, metal, etc.) so they can estimate whether the soil will fit in your space. Ask whether they charge by the cubic yard or by the load, and whether delivery includes spreading or just dropping it nearby.

If you're picking up bulk soil yourself, bring a tarp or plastic sheeting to lay down where the pile will sit. Soil stains concrete and kills grass underneath, so protect your driveway or lawn. Ask the supplier to wet the pile slightly before you load it—dry soil is dusty and harder to shovel.

For bagged soil, check the bag weight before you buy. A 2-cubic-foot bag of potting mix weighs 20 to 30 pounds, while a 2-cubic-foot bag of garden soil weighs 40 to 50 pounds. If you're carrying bags yourself, lighter potting mix may be worth the extra cost.

Frequently Asked Questions

Do I need to fill the bed all the way to the top?

No, but most gardeners fill it within 2 inches of the rim. Leaving space prevents soil from washing out when you water, but too much space wastes the bed's depth. Fill it to where you're comfortable watering without splashing soil onto the frame.

Can I reuse soil from last year?

Yes, but refresh it by mixing in 1 to 2 inches of compost or aged manure before planting. Old soil compacts and loses nutrients. If you had disease problems last year, replace the top 6 inches with fresh soil to reduce the risk of spreading pathogens.

What if my bed is not exactly 8 by 4 by 2?

Measure your actual interior dimensions and use the same formula: length × width × depth, then divide by 27 to convert cubic feet to cubic yards. If your bed is 7.5 × 3.8 × 2.2 feet, that's 63.3 cubic feet, or about 2.35 cubic yards. Round up to 2.5 to be safe.

Is it cheaper to buy soil in spring or fall?

Prices vary by region and supplier, but soil is often cheaper in fall when demand drops. Spring is busier, so suppliers may charge more and have longer delivery times. If you can wait until September or October, you may save money.

Can I mix different types of soil in the same bed?

Yes. Many gardeners layer cheaper garden soil on the bottom and potting mix or compost on top. This saves money while keeping the root zone light. Just make sure the bottom layer is at least 6 inches deep so roots have room to grow down.