Raised Bed Soil Calculator
Enter your bed size, depth, and mix — get the soil volume, bags per ingredient, weight, and the cheapest way to fill it.
Half topsoil, half compost — the all-purpose default.
Add 10% settling buffer (recommended) — beds sink as they settle, so order a little extra.
Fill the base with wood to save soil — keep at least 12″ of mix on top. (a method called hugelkultur)
Same volume, three ways to buy it — only “Blend it yourself” uses your recipe above.
Soil is heavy. Your fill weighs roughly 0.7–1.2 tons for this bed (1.30 yd³ of mix). One cubic yard of soil mix runs about 1,500–2,000 lbs — already near a half-ton truck's payload, so above that, delivery is usually the practical choice. Weight varies with moisture; check your truck's payload rating.
How deep does your bed need to be?
Minimum quality-mix depth by what you're growing — university extension data.
| Crops | Min depth | Examples |
|---|---|---|
| Shallow | 6″ | Lettuce, greens, herbs, radishes, spinach |
| Most vegetables | 8–12″ | Beans, cucumbers, broccoli, onions, beets |
| Deep-rooted | 18″+ | Tomatoes, peppers, carrots, parsnips, potatoes |
On a hard surface (concrete or patio) with no soil below, go deeper — University of Maryland Extension recommends at least 8″ for leafy greens and 12–24″ for deep-rooted crops. Source: University of Maryland Extension; University of Nebraska–Lincoln (USDA NRCS data).
How much soil common beds need.
Cubic feet of mix to fill standard raised bed sizes. Divide by 27 for cubic yards.
| Bed size | 6″ deep | 12″ deep | 18″ deep |
|---|---|---|---|
| 2 × 4 ft | 4 ft³ | 8 ft³ | 12 ft³ |
| 2 × 8 ft | 8 ft³ | 16 ft³ | 24 ft³ |
| 3 × 6 ft | 9 ft³ | 18 ft³ | 27 ft³ |
| 4 × 4 ft | 8 ft³ | 16 ft³ | 24 ft³ |
| 4 × 8 ft | 16 ft³ | 32 ft³ | 48 ft³ |
| 4 × 12 ft | 24 ft³ | 48 ft³ | 72 ft³ |
| 5 × 10 ft | 25 ft³ | 50 ft³ | 75 ft³ |
Pure geometry (length × width × depth), Decimal-verified. Your bag and cost counts appear in the calculator above.
What is raised bed soil — and why not just use dirt?
Raised bed soil is a blend of topsoil and compost — usually with some coarse sand mixed in — not the dirt dug from your yard. It's built to stay loose, drain well, and feed your plants. A 4-by-8-foot bed filled 12 inches deep needs about 32 cubic feet of it, or roughly 1.2 cubic yards.
The real advantage of a raised bed is control: you decide what fills it. That matters most when your native soil is compacted, poorly drained, or contaminated — common reasons to build a bed in the first place. That said, don't assume the dirt in your yard is useless. Good native soil grows vegetables just fine, so dig a test hole first; if you can get down 12 inches without hitting hardpan or rock, you may not need much imported soil at all. Washington State University Extension.
If you're growing food, get a basic soil test before planting — and have it checked for lead, since older urban and roadside soils can carry it. University of Maryland Extension.
One thing to avoid: filling a bed with pure compost. Too much organic matter packs down, holds too much water, and throws off the balance — University of Maryland Extension puts the target at 25–50% organic matter by volume, not 100%. The rest is topsoil. Use the calculator above to get your exact volume, then see the mix options below.
How deep should a raised bed be?
Most vegetables need 8 to 12 inches of soil. Shallow crops like lettuce and herbs do fine in 6 inches, while deep-rooted ones like tomatoes, peppers, and carrots want 18 inches or more. The depth guide above breaks it down by crop.
One catch: those depths assume the bed sits on open ground, where roots grow past the frame into the dirt below. If your bed sits on a patio, deck, or concrete, go deeper — University of Maryland Extension recommends at least 8 inches for leafy greens, beans, and cucumbers on a hard surface, and 12 to 24 inches for peppers, tomatoes, and squash. University of Maryland Extension; University of Nebraska–Lincoln.
And soil settles: raised bed soil subsides over time as compost breaks down and rain packs it in, so plan to top it off periodically to keep the full depth — or just leave the calculator's settling buffer on. Washington State University Extension.
How much soil do you need?
The math is simple: multiply length × width × depth in feet to get cubic feet, then divide by 27 for cubic yards.
So a 4-by-8-foot bed, 12 inches deep, works out to 4 × 8 × 1 = 32 cubic feet, or about 1.2 cubic yards. To turn that into bags, divide your cubic feet by the bag size and round up — stores don't sell half a bag. The calculator above does all of this for you, including the bag math for each ingredient.
Got an odd shape? Break it into pieces. An L-shaped bed is two rectangles added together; a round bed uses the diameter. And always round up: a leftover half-bag beats running out halfway through on a Saturday.
What's the best soil mix for a raised bed?
There's no single right recipe, but extension services agree on the building blocks: topsoil for structure, compost for nutrients, and sometimes coarse sand for drainage. The calculator gives you three options:
Balanced (50/50) — equal parts topsoil and compost. A solid all-purpose mix; University of Maryland Extension recommends a 1:1 compost-to-topsoil blend.
Budget (70/30) — about 70% topsoil, 30% compost. Cheaper because compost costs more than topsoil, and Iowa State University Extension lists it as a good option.
Drainage (3-way) — equal parts topsoil, compost, and coarse sand. Best for heavy or poorly draining sites; both Iowa State and Oregon State Extension recommend this equal-parts mix. University of Maryland, Iowa State, and Oregon State Extension.
One thing every source agrees on: don't fill a bed with pure compost. It packs down, holds too much water, and throws off the nutrient balance — aim for 25–50% organic matter by volume, not 100%.
Want to use less soil? You can fill the bottom of a deep bed with logs and branches before adding your mix — a method called hügelkultur. It cuts how much soil you buy. Just know the trade-off: Washington State University notes the evidence is thin, the bed sinks as the wood decays, and you'll likely rebuild it in five to six years. Whichever mix you pick, expect it to settle, so top off with compost periodically to keep the bed full. Washington State University Extension.
Raised bed soil vs. potting soil vs. topsoil
These three get mixed up constantly, and using the wrong one is a common first-bed mistake.
Raised bed soil is the blend we've been describing — topsoil plus compost, sometimes with sand. It has the body to hold roots and the nutrients to feed them. This is what fills a bed.
Potting soil (or "potting mix") is lightweight and soilless — usually peat or coconut coir with perlite or vermiculite. It's built for containers, where drainage and weight matter most. In a big raised bed it's expensive and dries out fast; Washington State University notes these peat-and-vermiculite mixes cost more and seldom do better than a simple soil-and-compost blend.
Topsoil sold in bags is mineral soil — good structure, but little nutrition on its own, and it packs down without organic matter. Quality also varies: what's labeled "topsoil" is often really landscaping fill, so look at it before you buy. Washington State University Extension. Topsoil makes a great base, but only once compost is mixed in — which is exactly what raised bed soil is.
Short version: topsoil + compost = raised bed soil. Potting mix is a different product for a different job.
Should you buy bagged, mix your own, or order bulk?
It comes down to how much you need. Bagged raised-bed soil is the easiest — grab ready-made bags and go. It's the priciest per cubic foot, so it fits one small bed. Mixing your own from separate bags of topsoil, compost, and sand costs less per cubic foot and lets you control the recipe — best for a mid-size bed or two. Bulk delivery by the cubic yard is cheapest per unit, but landscape yards usually have an order minimum and a flat delivery fee, so it only pays off at larger volumes.
The calculator above prices all three side by side using your numbers, so you can see exactly where the line falls. As a rule of thumb, bulk starts winning somewhere above a cubic yard.
Frequently asked questions.
How much soil do I need for a 4×8 raised bed?
A 4-by-8-foot bed filled 12 inches deep needs about 32 cubic feet of soil — roughly 1.2 cubic yards. At 6 inches deep, it's half that. Enter your own dimensions in the calculator above for an exact figure.
How deep should a raised bed be?
Most vegetables need 8 to 12 inches of soil. Lettuce and herbs are fine in 6 inches, while deep-rooted crops like tomatoes, peppers, and carrots want 18 inches or more. If the bed sits on a hard surface with no soil below, go deeper.
What's the best soil mix for a raised bed?
A 50/50 blend of topsoil and compost works for most beds. For heavy or poorly draining soil, use equal parts topsoil, compost, and coarse sand. The one rule every extension service agrees on: never fill a bed with pure compost.
Can I use potting soil or garden soil in a raised bed?
Potting soil is too light and too expensive to fill a full bed, and it dries out fast. Bagged "garden soil" and plain topsoil work only once you mix compost into them. Raised bed soil — topsoil plus compost — is what you actually want.
Is the drainage 3-way mix cheaper?
No — adding coarse sand makes it the most expensive mix per cubic foot, because bagged sand is dense and costs more per cubic foot than topsoil or compost. Use the 3-way mix for drainage in heavy or clay situations, not to save money.
Why add a settling buffer?
Fresh mixes — especially compost-heavy ones — settle as organic matter breaks down and air pockets close, so a bed can drop noticeably in its first season. Ordering about 10% extra means you won't come up short, with a little left to top off periodically as the bed keeps settling.
Can I reuse old raised bed soil?
Yes. Raised bed soil subsides as it settles and breaks down, so each season just top it off with a fresh inch or two of compost to bring it back to full depth. There's no need to replace it.
Do I have to fill the whole bed with soil?
No. You can fill the bottom of a deep bed with logs and woody debris — a method called hügelkultur — then top it with soil mix, which cuts how much soil you buy. It can work, though the science is thinner than its fans claim. Keep at least 12 inches of quality mix on top so roots have room to grow.
How much soil fits in a pickup truck?
Less than you'd think. A full-size pickup holds about 2.5 cubic yards of mulch, but soil is two to four times heavier — by weight you're limited to roughly one cubic yard of soil mix before you hit a typical half-ton truck's payload. For anything more, delivery is usually the better call.
How much does it cost to fill a raised bed?
It depends on your mix and whether you buy bagged or bulk. Use the cost comparison in the calculator above — it prices bagged, mix-your-own, and bulk side by side. As a rule of thumb, bulk delivery wins once you're filling more than about a cubic yard.
Methodology & sources
Every formula and number on this page traces to a university extension publication or to typical US retail pricing. Volume uses standard area-by-depth geometry (27 cubic feet = 1 cubic yard); the optional 10% settling buffer, the mix recipes, and the weight range all trace to the sources below. All math is Decimal-verified.
Mix ratios and bed depth
- University of Maryland Extension — Soil to Fill Raised Beds — link
- Iowa State University Extension — What Would Be a Good Soil Mix for a Raised Bed? — link
- Oregon State University Extension — EM 9308: How to Use Compost in Gardens and Landscapes — link
- University of Nebraska–Lincoln Extension — G2189 (effective root zone; USDA NRCS data) — link
Soil weight (bulk density)
- University of Maryland Extension — Organic Matter and Soil Amendments — link
- USDA Natural Resources Conservation Service — Soil Bulk Density, Moisture, and Aeration — link
Settling and wood-fill (hugelkultur)
- Washington State University Extension — FS075E: Raised Beds — Will They Benefit Your Vegetable Garden — link
- Washington State University Extension — FS283E: Hügelkultur — What Is It, and Should It Be Used in Home Gardens? — link
Pricing. The bagged, bulk, and delivery prices are pre-filled with typical US retail and landscape-supply figures and are fully editable — replace them with your local quote for an exact estimate.
Last methodology review: June 2026.
Independence: Sources are cited for reference only. The universities, agencies and retailers named on this page do not sponsor or endorse MaterialCalcs, and we are not affiliated with them. Retail prices were checked by hand and vary by store and region.