How Much Soil Do I Need for a Raised Garden Bed?

Quick answer: Multiply length × width × height (all in feet) to get cubic feet. A standard 4×8 foot raised bed that's 12 inches deep needs 32 cubic feet of soil — about 1.2 cubic yards or 21 bags of 1.5 cu ft bagged soil.

Skip the math — use our free Raised Bed Soil Calculator →

The Formula (Step by Step)

Measure your bed — length, width, and height in feet
Convert height to feet if needed — 12 inches = 1 ft, 18 inches = 1.5 ft
Multiply: L × W × H = cubic feet
Convert to cubic yards (for bulk orders) — divide by 27

Common Raised Bed Sizes

4×4 × 12" deep: 16 cu ft (0.59 cu yd)
4×8 × 12" deep: 32 cu ft (1.19 cu yd)
4×8 × 18" deep: 48 cu ft (1.78 cu yd)
3×6 × 12" deep: 18 cu ft (0.67 cu yd)
4×12 × 12" deep: 48 cu ft (1.78 cu yd)

Circular Beds

Use π × radius² × depth. A 6-foot diameter bed, 12 inches deep:
3.14 × 3² × 1 = 28.3 cu ft (1.05 cu yd)

What Soil Mix Should I Use?

The most popular mix for raised beds is the "Mel's Mix" (from Square Foot Gardening):

⅓ compost (mixed types — mushroom, manure, leaf)
⅓ peat moss or coconut coir
⅓ vermiculite or coarse perlite

A simpler and cheaper approach that works great:

60% topsoil
30% compost
10% perlite or coarse sand (for drainage)

Don't use 100% garden soil or topsoil. It compacts too much in raised beds and drains poorly. Mixing in compost and an aerator makes a huge difference.

Bags vs. Bulk Soil

Bags (1–1.5 cu ft): $5–$10 each. Convenient for one small bed.
Bulk (cubic yard): $30–$60 per yard + $50–$100 delivery. Way cheaper for large orders.

Break-even point: If you need more than 1 cubic yard, bulk delivery saves money. For a single 4×8 bed, bags and bulk are roughly the same cost.

Common Mistakes to Avoid

❌ Not accounting for settling

Fresh soil settles 10–20% in the first few weeks. Fill your bed to the top — it'll drop. You'll likely need to top up in year two as organic matter decomposes.

❌ Using only bagged "garden soil"

Bagged garden soil is designed as an amendment, not a standalone fill. It's often too dense for raised beds. Mix it with compost and perlite at minimum.

❌ Filling deep beds entirely with expensive soil

For beds taller than 18 inches, use the "Hügelkultur" method: fill the bottom half with logs, branches, leaves, and cardboard. Then fill the top 12–18 inches with quality soil. Saves money and improves drainage.

❌ Forgetting drainage

Raised beds should drain freely from the bottom. If your bed sits on concrete or compacted clay, drill holes or add a gravel layer before filling with soil.

Pro Tips

Buy compost in bulk from a local landscape supply yard. It's 5–10× cheaper than bagged.
Start a compost pile now. Next year's top-up will be free.
Soil test: Spend $15 on a soil test from your local extension office before planting. It tells you exactly what amendments to add.
Coconut coir is a sustainable alternative to peat moss. It comes in compressed bricks — one brick expands to about 8–9 cu ft.

Frequently Asked Questions

How deep should a raised bed be?

12 inches is ideal for most vegetables. Carrots and potatoes prefer 18 inches. Lettuce and herbs do fine in 6–8 inches. Deeper isn't always better — it just costs more soil.

Can I reuse soil from last year?

Absolutely. Top up with 1–2 inches of compost each spring to replace nutrients and organic matter that decomposed. Replace soil completely only if you had serious disease issues.

How much does a cubic yard of soil weigh?

About 1,800–2,200 lbs depending on moisture. A full pickup truck bed holds about 1–2 cubic yards. Don't overload your vehicle — that's a lot of weight.

Should I put anything on the bottom of a raised bed?

Cardboard or landscape fabric on the bottom blocks weeds from growing up. Don't use plastic — it traps water. If gophers are a problem, use hardware cloth (wire mesh) on the bottom.

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