A 4x8 raised bed needs 32 cubic feet of soil, or about 1.2 cubic yards
The amount of dirt you need depends on how deep you want to fill it. A standard 4-foot by 8-foot raised bed that is 12 inches deep requires 32 cubic feet of soil. If your bed is deeper — say 18 inches — you'll need 48 cubic feet. If it's shallower at 8 inches, you'll need about 21 cubic feet.
The math is straightforward: length × width × depth (all in feet) = cubic feet. For a 4×8 bed at 12 inches deep, that's 4 × 8 × 1 = 32 cubic feet. Most garden centers and landscape suppliers sell soil by the cubic yard, which equals 27 cubic feet. So 32 cubic feet is roughly 1.2 cubic yards — most people order 1.5 yards to account for settling and to have a little extra on hand.
Soil settles over time, especially in the first season. You'll notice the level drop by 1 to 2 inches within the first few weeks as the material compacts. This is normal and expected.
Key Takeaways
- A 4x8 raised bed that is 12 inches deep holds 32 cubic feet of soil, which is about 1.2 cubic yards.
- Multiply length × width × depth in feet to find your exact cubic footage, then divide by 27 to convert to cubic yards.
- Most suppliers sell soil in bags (typically 2 cubic feet each) or by the cubic yard; ordering 1.5 yards gives you a buffer for settling and overfill.
- Soil compacts and settles in the first few weeks, so expect the level to drop slightly after planting.
- The depth you choose affects the total amount: 8 inches deep needs 21 cubic feet, 12 inches needs 32, and 18 inches needs 48.
Calculating soil for different bed depths
The depth of your raised bed is the biggest variable. Most gardeners use 12 inches as a standard because it's deep enough for most vegetables, herbs, and shallow-rooted perennials, but not so deep that it wastes soil or becomes hard to reach the center.
If you're growing root vegetables like carrots, parsnips, or beets, 12 inches is the minimum. For leafy greens, herbs, and shallow-rooted flowers, 8 inches works fine. If you want to grow deeper-rooted crops like tomatoes or peppers, or if you're building on top of compacted clay or poor soil, 18 inches is better.
| Bed Depth | Cubic Feet Needed | Cubic Yards Needed | Approximate Bags (2 cu ft each) |
|---|---|---|---|
| 8 inches | 21 cubic feet | 0.78 cubic yards | 11 bags |
| 12 inches | 32 cubic feet | 1.2 cubic yards | 16 bags |
| 18 inches | 48 cubic feet | 1.78 cubic yards | 24 bags |
Buying soil in bags versus by the yard
For a 4×8 bed, buying by the cubic yard is almost always cheaper than buying bags. A cubic yard of soil typically costs $30 to $60 depending on quality and your location, while 27 bags of 2-cubic-foot soil (the equivalent) can run $50 to $100 or more. The trade-off is delivery and handling — a cubic yard arrives in a pile that you have to shovel into the bed, whereas bags are easier to move if you have a small space or no vehicle access.
If you order by the yard, ask the supplier whether they deliver or whether you pick it up. Some landscape suppliers include delivery for orders over a certain amount; others charge a flat fee. A cubic yard of soil weighs roughly 1,000 to 1,500 pounds depending on moisture content, so it's not practical to transport in a standard car.
Bagged soil makes sense if you're filling a bed in stages, if you want to blend different types (like adding compost or potting mix to garden soil), or if you have no way to receive a bulk delivery. Buy bags labeled "garden soil" or "topsoil" rather than potting mix, which is lighter and more expensive.
What type of soil to use
You don't need to use pure topsoil. Many gardeners use a blend: about 60% garden soil or topsoil, 30% compost, and 10% perlite or coarse sand for drainage. This mix is richer than straight topsoil and drains better than pure compost.
If you're starting from scratch and want a straightforward approach, buy a garden soil blend — most suppliers offer a mix designed specifically for raised beds that already includes compost and other amendments. These cost a bit more per yard but save you the work of blending.
Avoid pure potting mix for a large raised bed; it's designed for containers and will dry out too quickly in an open bed. Also avoid "fill dirt" or "construction soil," which is often compacted clay with little organic matter.
Accounting for settling and future amendments
Soil settles as it absorbs water and as organisms break down organic matter. In the first season, expect 1 to 2 inches of drop. In subsequent years, the bed will settle less, but you'll still lose some volume as compost decomposes.
Many gardeners top-dress their raised beds each spring with 1 to 2 inches of fresh compost. This replenishes organic matter and keeps the soil level consistent. If you plan to do this, you might order slightly more soil initially so you're not starting with a bed that's already half-full after settling.
If you're filling a bed for the first time and want it to be full and ready to plant when ready, order 1.5 cubic yards instead of 1.2. The extra soil gives you a cushion for settling and for that first season of top-dressing.
Delivery and logistics for bulk soil orders
When you order soil by the yard, the supplier will ask about access to your garden. They need to know whether a dump truck can reach your raised bed or whether the soil will be dropped at the curb and you'll have to move it yourself. A standard dump truck is about 8 feet wide, so if your driveway or gate is narrower, let the supplier know — they may send a smaller truck or drop the load in your front yard.
Soil is heavy and wet. If it rains before delivery, the load will weigh more and may be harder to spread. If possible, schedule delivery for a dry day or a day when rain isn't forecast. Have a shovel, wheelbarrow, and a few hours set aside to move the soil into the bed.
If you're ordering multiple cubic yards for several beds, ask whether the supplier offers a discount. Some do for orders over 3 or 4 yards.
Frequently Asked Questions
Can I use less soil if I put cardboard or newspaper under the bed?
Cardboard or newspaper at the bottom doesn't reduce the amount of soil you need — it just prevents weeds from growing up through the bottom. You still need 32 cubic feet to fill a 12-inch-deep 4×8 bed. The cardboard layer is typically only a few inches thick and will decompose over time anyway.
What if my raised bed is a different size than 4x8?
Use the formula: length (in feet) × width (in feet) × depth (in feet) = cubic feet. Then divide by 27 to get cubic yards. For example, a 3×6 bed at 12 inches deep is 3 × 6 × 1 = 18 cubic feet, or 0.67 cubic yards. Most online calculators can do this for you if you enter your dimensions.
Should I fill the bed all the way to the top?
Leave about 1 to 2 inches of space at the rim so water doesn't spill over the edge when you water. This means if your bed is 12 inches tall, fill it to about 10 to 11 inches. The soil will settle a bit anyway, so you'll end up with a level surface after a few weeks.
Can I reuse soil from year to year?
Yes. At the end of the season, you can keep the soil in the bed and top it with fresh compost the next spring. Over several years, the soil will become richer as organic matter accumulates. You don't need to replace it entirely unless it becomes compacted or depleted, which usually takes 3 to 5 years of heavy use.
How do I know if I ordered too much soil?
Extra soil can be spread around the base of trees or shrubs, used to level low spots in the yard, or stored in bags for future amendments. It's better to have a little left over than to run short and have to make another trip to the supplier.