By Azura · Updated June 2026 · Raised Garden Hub is reader-supported. When you buy through links on our site, we may earn an affiliate commission at no extra cost to you.
A 4×8 ft raised bed needs 32 cubic feet of soil at 12 inches deep — about 22 bags (1.5 cu ft each), or just over 1 cubic yard. Here are exact numbers for every common depth, plus how to fill it for less.
The formula (works for any bed size)
Soil volume = length × width × depth, all measured in feet. Because depth is usually given in inches, divide it by 12 first.
4×8 at 12 inches: 4 × 8 × (12 ÷ 12) = 4 × 8 × 1 = 32 cubic feet
4×8 at 6 inches: 4 × 8 × (6 ÷ 12) = 4 × 8 × 0.5 = 16 cubic feet
To convert cubic feet to cubic yards, divide by 27 (there are 27 cubic feet in one cubic yard).
To find bags, divide cubic feet by the bag size. A common 1.5 cu ft bag: 32 ÷ 1.5 ≈ 21.3 — round up to 22 bags.
Rule of thumb: Always add 10% to your total. Soil settles 1–2 inches in the first season, and a slightly overfilled bed is far better than a short one.
For any odd size, plug your numbers into the soil calculator — it outputs cubic feet, yards, and bag counts instantly.
4×8 raised bed soil by depth
| Depth | Cubic feet | Cubic yards | Bags (1.5 cu ft) | Bags (2 cu ft) |
|---|---|---|---|---|
| 6 in | 16 | 0.59 | ~11 | ~8 |
| 10 in | 26.7 | 0.99 | ~18 | ~14 |
| 12 in | 32 | 1.19 | ~22 | ~16 |
| 18 in | 48 | 1.78 | ~32 | ~24 |
Not sure which depth is right for what you’re growing? How deep should a raised garden bed be breaks it down by crop type.
Other common bed sizes
If you’re not building a 4×8, the same formula applies. Here are two other popular sizes calculated at 12-inch depth:
| Bed size | Cubic feet | Cubic yards | Bags (1.5 cu ft) |
|---|---|---|---|
| 4×4 | 16 | 0.59 | ~11 |
| 2×8 | 16 | 0.59 | ~11 |
| 4×8 | 32 | 1.19 | ~22 |
| 4×12 | 48 | 1.78 | ~32 |
A 4×4 and a 2×8 hold the same volume (both are 16 cu ft at 12 inches deep) — a useful reminder that only length × width × depth matters, not the shape.
Bags vs. bulk delivery
Bags are convenient for smaller orders under about 1.5 cubic yards. You can buy exactly what you need, store leftovers, and pick up quality mixes from a garden center. The downside is cost — bagged mix typically runs $8–$15 per 1.5 cu ft bag, which adds up fast on a deep bed.
Bulk by the yard becomes cheaper once you need 1–2+ cubic yards. A local landscape supplier will deliver a yard or more of quality blend (often called “garden mix” or “raised bed mix”) for a fraction of the per-cubic-foot bag price. The catch: you need somewhere to put it and a way to move it, so have a wheelbarrow ready.
For a standard 12-inch 4×8 bed at 1.19 cubic yards, bags and bulk are fairly close in effort. For an 18-inch deep bed at 1.78 cubic yards, bulk delivery usually wins on price. See our guide on how to fill a raised garden bed for a full cost comparison and recommended mix ratios.
How to fill a deep bed for less
A deep 18-inch bed holds 48 cubic feet of soil — that’s a lot of mix to buy. The good news: plant roots mostly stay in the top 12 inches, so you don’t need premium mix all the way down.
Use bottom filler to reduce how much soil you buy:
- Logs, branches, and wood chunks (hugelkultur approach)
- Leaves, straw, or untreated cardboard
- Coarse wood chips or pine bark nuggets
- Broken-up sod (grass side down)
Fill the bottom 6–8 inches with this material, then add your quality soil mix on top. On an 18-inch bed, this can cut your soil purchase from 48 cu ft down to roughly 27–32 cu ft — saving you 8–10 bags.
Learn more about this approach in the hugelkultur raised bed guide and what to put at the bottom of a raised garden bed.
What kind of soil to use
Once you know how much you need, the next question is what to fill it with. A standard raised bed mix is not garden soil — it’s lighter, drains better, and supports root growth. A classic recipe is one-third compost, one-third peat moss or coco coir, and one-third coarse perlite or vermiculite (often called Mel’s Mix).
For a detailed breakdown of what works best and what to avoid, see best soil mix for raised garden beds.
Quick reference
- 4×8 at 6 in: 16 cu ft — about 11 bags (1.5 cu ft)
- 4×8 at 12 in: 32 cu ft — about 22 bags (1.5 cu ft) or 1.2 cu yd bulk
- 4×8 at 18 in: 48 cu ft — about 32 bags (1.5 cu ft) or 1.8 cu yd bulk
- Add 10% for settling
- Deep beds: use bottom filler to reduce soil cost by up to 40%
Next steps
- Not sure how deep to go? See how deep a raised bed should be.
- Choosing a bed first? See the best raised garden beds of 2026.
- Ready to fill? Check how to fill a raised garden bed for step-by-step instructions.
Frequently asked questions
How many cubic feet of soil does a 4x8 raised bed need at 12 inches deep?
A 4x8 bed at 12 inches deep holds exactly 32 cubic feet of soil (about 1.19 cubic yards). Plan to buy around 10% extra to account for settling in the first season.
How much soil for a 4x8 raised bed that's 6 inches deep?
16 cubic feet, which is roughly 0.59 cubic yards or about 11 bags of 1.5-cubic-foot soil. A 6-inch depth works well for shallow-rooted crops like lettuce and herbs.
How much soil for a 4x8 raised bed that's 18 inches deep?
48 cubic feet, or about 1.78 cubic yards. That's 32 bags of 1.5-cubic-foot mix. For a bed this deep, filling the bottom 6 inches with logs and leaves can cut your soil cost significantly.
How many bags of soil do I need for a 4x8 raised bed?
For a standard 12-inch-deep bed, you need about 22 bags of 1.5-cubic-foot mix, or about 16 bags of 2-cubic-foot mix. For a 6-inch bed, roughly 11 bags (1.5 cu ft) or 8 bags (2 cu ft).
How many cubic yards of soil for a 4x8 raised bed?
At 12 inches deep you need about 1.19 cubic yards. At 6 inches it's roughly 0.59 cubic yards. If you're ordering bulk delivery, 1.25 yards covers a 12-inch bed with a little extra for settling.
How can I spend less money filling a deep 4x8 raised bed?
Fill the bottom 6 to 8 inches with logs, branches, straw, or leaves, then use quality soil mix for the top 10 to 12 inches where roots actually grow. This hugelkultur approach can cut your soil purchase in half on an 18-inch-deep bed.