How Much Soil for a Raised Bed?
Calculate the exact amount of soil for raised garden beds. Get results in cubic feet, cubic yards, and number of bags with cost estimates.
Quick Answer
A 4×8 ft raised bed filled 12 inches deep needs about 1.19 cubic yards (32 cubic feet) of soil mix, costing roughly $35–$65 for bulk or $80–$160 in bags.
Enter your dimensions above to calculate raised bed soil needed.
💡 A standard 4×8 ft raised bed at 12 inches deep needs about 1.19 cubic yards of soil mix
How to Calculate Raised Bed Soil Needed
Formula
Length (ft) × Width (ft) × Depth (in) ÷ 324 = Cubic Yards
Multiply your raised bed's inside length by inside width to get the area. Multiply by depth in inches, then divide by 324 to convert to cubic yards. For bags, multiply cubic yards by 27 to get cubic feet.
Example
For a 4 ft × 8 ft raised bed filled 12 inches deep: 4 × 8 × 12 ÷ 324 = 1.19 cubic yards (about 32 cu ft). That's roughly 21 bags of 1.5 cu ft soil mix.
Tips & Best Practices
- •Use a 60/30/10 mix: 60% topsoil, 30% compost, 10% aeration (perlite or vermiculite).
- •For beds taller than 18 inches, fill the bottom third with logs, branches, or straw (hügelkultur) to save on soil.
- •Soil in raised beds settles 10–20% in the first season — fill to the brim and top off in spring.
- •Bagged soil is convenient but bulk delivery is 40–60% cheaper for two or more beds.
- •Avoid using only topsoil — it compacts in raised beds. Always mix in compost for drainage and nutrients.
Quick Reference
A standard 4×8 ft raised bed at 12 inches deep needs about 1.19 cubic yards of soil mix
How Much Soil Do I Need? Volume by Bed Size
The most common raised bed sizes are 4×4, 4×8, and 3×6 feet. Below is a quick reference for how much soil each standard size needs at popular fill depths.
These estimates assume you're filling the full depth with soil mix. For beds taller than 18 inches, you can reduce costs by layering branches or straw in the bottom third.
| Bed Size | 8" Deep | 12" Deep | 18" Deep |
|---|---|---|---|
| 3×6 ft | 0.33 yd³ (9 cu ft) | 0.67 yd³ (18 cu ft) | 1.0 yd³ (27 cu ft) |
| 4×4 ft | 0.40 yd³ (10.7 cu ft) | 0.59 yd³ (16 cu ft) | 0.89 yd³ (24 cu ft) |
| 4×8 ft | 0.79 yd³ (21.3 cu ft) | 1.19 yd³ (32 cu ft) | 1.78 yd³ (48 cu ft) |
| 4×12 ft | 1.19 yd³ (32 cu ft) | 1.78 yd³ (48 cu ft) | 2.67 yd³ (72 cu ft) |
| 2× 4×8 ft beds | 1.58 yd³ (42.6 cu ft) | 2.37 yd³ (64 cu ft) | 3.56 yd³ (96 cu ft) |
Soil settles 10–20% in the first growing season. Fill beds to the brim and plan to top off next spring.
Best Soil Mix for Raised Beds
Don't fill raised beds with straight topsoil — it compacts, drains poorly, and starves plant roots of oxygen. A blended mix is essential.
The ideal mix depends on what you're growing. Here are the two most popular approaches, both proven by decades of gardening results.
Standard Mix (60/30/10)
Best for most vegetable gardens and flower beds. Provides good drainage while retaining enough moisture for consistent growth.
- 60% Screened topsoil
- 30% Compost (aged, well-rotted)
- 10% Perlite, vermiculite, or coarse sand
Mel's Mix (Square Foot Gardening)
Lighter and faster-draining. Popular for intensive small-space gardening. More expensive upfront but virtually weed-free.
- 1/3 Peat moss (or coconut coir)
- 1/3 Compost (mix of 5+ sources)
- 1/3 Coarse vermiculite
Bulk vs. Bagged
Bulk delivery ($30–$55/yd³) is 40–60% cheaper than bagged soil ($5–$8 per 1.5 cu ft bag). If you have two or more beds, bulk is almost always worth it. One cubic yard fills a standard 4×8 bed at 10 inches deep.
How Deep Should a Raised Bed Be?
Soil depth matters more than bed width. Most vegetables need at least 12 inches to thrive — but the right depth depends on what you're growing.
Below are recommended minimum depths by crop type. Deeper is generally better — roots don't stop at the minimum.
| Bed Depth | Best For |
|---|---|
| 6 inches | Lettuce, herbs, radishes, strawberries |
| 8–10 inches | Peppers, beans, peas, most flowers |
| 12 inches | Tomatoes, cucumbers, squash, most vegetables |
| 18–24 inches | Carrots, potatoes, parsnips, sweet potatoes |
Filling a tall bed on a budget? For beds 18 inches or taller, use the hügelkultur method: fill the bottom third with logs, branches, and leaves, then top with soil mix. This saves 30–40% on soil while improving drainage.
Raised Bed Soil Cost: Bulk vs. Bags
Soil is usually the biggest cost of a raised bed project. Here's a realistic comparison for the most popular bed size.
| Method | Cost for 4×8 Bed (12" deep) | Notes |
|---|---|---|
| Bulk soil mix | $35–$65 | + $50–$150 delivery |
| Bagged garden soil | $105–$168 | ~21 bags × $5–$8 each |
| DIY mix (bulk components) | $45–$80 | Topsoil + compost + perlite separately |
Bulk delivery makes sense for 2+ beds. For a single small bed, bagged soil from a garden center may be simpler despite the higher per-yard cost.
Need just the topsoil component? Use our topsoil calculator →
Frequently Asked Questions
How much soil do I need for a 4×8 raised bed?+
A 4×8 ft raised bed at 12 inches deep needs 32 cubic feet (about 1.19 cubic yards) of soil. That's roughly 21 bags of 1.5 cu ft soil mix, or about one cubic yard of bulk delivery.
How much soil do I need for a 4×4 raised bed?+
A 4×4 ft raised bed at 12 inches deep needs 16 cubic feet (about 0.59 cubic yards) of soil. That's roughly 11 bags of 1.5 cu ft soil mix.
What's the best soil mix for raised beds?+
The most popular mix is 60% topsoil, 30% compost, and 10% perlite or vermiculite. For square foot gardening, Mel's Mix (1/3 peat moss, 1/3 compost, 1/3 vermiculite) is a proven option. Avoid 100% topsoil — it compacts too much in raised beds.
How deep should a raised bed be?+
Most vegetables need 12 inches of soil depth. Shallow-rooted crops (lettuce, herbs) grow fine in 6–8 inches. Deep-rooted crops (tomatoes, carrots) benefit from 18–24 inches.
How much does raised bed soil cost?+
Bulk soil mix costs $30–$55 per cubic yard. Bagged raised bed soil runs $5–$8 per 1.5 cu ft bag. A single 4×8 bed costs roughly $35–$65 bulk or $105–$168 in bags.
Should I put anything in the bottom of a raised bed?+
For beds under 12 inches tall, fill entirely with soil mix. For taller beds (18–24 inches), you can layer logs, branches, or straw in the bottom third to reduce soil volume and improve drainage (hügelkultur method).