Raised Garden Bed Soil Calculator
Figure out exactly how much soil you need for your raised beds — in cubic feet, cubic yards, liters, and bags. Plus, calculate custom topsoil, compost, and amendment mixes.
📐 Bed Dimensions
Accounts for settling & compaction.
🧪 Soil Mix Ratio (optional)
🌻 Your Soil Estimate
Volume
0
cubic feet
Cubic yards
0
cu yd
Liters
0
L
Bags needed
0
at 1 cu ft each
🧪 Component Mix Breakdown
Topsoil
0 cu ft
Compost
0 cu ft
Other amendment
0 cu ft
💡 Tip: Soil settles after watering. The top-off allowance adds extra volume to compensate. Bulk soil is usually sold by the cubic yard; bagged soil is sold by cubic feet.
How to Calculate Soil for a Raised Garden Bed
A raised garden bed soil calculator takes the guesswork out of filling your beds. The basic formula is simple: volume = length × width × depth. But real-world gardening adds nuance — soil settles, you might want a custom compost mix, and bulk vs. bagged soil changes how you buy. This tool handles all of it.
Soil Volume Calculation
Most raised beds are rectangular, so the volume formula is straightforward. For example, an 8 ft × 4 ft bed that is 10 inches deep needs 8 × 4 × (10/12) ≈ 26.7 cubic feet of soil. Our garden bed fill calculator does this instantly and also converts to cubic yards and liters, so you can order confidently whether you're buying bags or a bulk delivery.
Bed Dimensions & Depth
Depth matters more than length or width for root health. Shallow beds (6–8 inches) work for lettuce, herbs, and radishes. Deeper beds (10–12 inches) suit tomatoes, carrots, and peppers. If your bed sits on native soil, you can sometimes use less soil because roots can penetrate downward — but many gardeners still fill the full depth for consistent drainage and weed suppression.
Soil Settling & Top-Off Allowance
Fresh soil mixes are fluffy. After a few waterings, they settle by 10–20%. Our calculator includes an optional top-off allowance (default 10%) so you buy enough soil the first time. Skipping this often means a second trip to the store mid-season.
Bag vs. Bulk Soil
Bagged soil is sold in cubic feet (0.75, 1, 1.5, 2, or 3 cu ft bags). Bulk soil is sold by the cubic yard (27 cubic feet). For small beds, bags are convenient. For large projects — say, more than 1 cubic yard — bulk delivery is usually far cheaper per cubic foot. This cubic yard soil calculator shows both so you can compare.
Compost Ratios & Soil Mixes
There is no single "best" soil recipe. A common starting point is 60% topsoil, 30% compost, 10% amendment (like perlite or aged manure), but this varies by crop, climate, and what's locally available. Heavy clay topsoil needs more compost; sandy soil benefits from more organic matter. Use the mix panel above to test different ratios and see exactly how many cubic feet of each component you need. Always test your soil and adjust over time.
Practical Filling Considerations
- Place cardboard or newspaper at the bottom to suppress weeds — it decomposes over time.
- Don't over-compact the soil; roots need air pockets.
- Water thoroughly after filling to help settling before planting.
- Leave 1–2 inches of headspace below the rim to avoid overflow when watering.
- For very deep beds (over 18 inches), you can fill the bottom with logs, branches, or leaves to save soil — this is called "hügelkultur."
Frequently Asked Questions
How much soil do I need for a 4×8 raised bed? ▼
A 4 ft × 8 ft bed that is 10 inches deep needs about 26.7 cubic feet of soil (8 × 4 × 10/12). With a 10% top-off allowance, plan for roughly 29.3 cubic feet — that's about 30 bags of 1 cu ft soil, or just over 1 cubic yard.
How many bags of soil equal a cubic yard? ▼
One cubic yard equals 27 cubic feet. So you'd need 27 bags of 1 cu ft soil, 18 bags of 1.5 cu ft, or 14 bags of 2 cu ft soil to make a cubic yard. For projects over 1 cubic yard, bulk delivery is usually more economical.
What is the best soil mix for a raised garden bed? ▼
There's no universal recipe — it depends on your crops, climate, and existing soil. A widely used starting point is 60% topsoil, 30% compost, 10% perlite or aged manure. Vegetables generally thrive with more compost (up to 40–50%), while root crops prefer looser, sandier mixes. Test your soil and adjust each season.
Should I put rocks or gravel at the bottom of my raised bed? ▼
Generally, no. A gravel layer creates a "perched water table" that can keep the soil above it waterlogged. Unless your bed is extremely deep and you're using the hügelkultur method (logs and branches at the bottom), it's better to fill the entire bed with soil or use a weed barrier fabric at the base.
How deep should a raised garden bed be? ▼
It depends on what you're growing. 6–8 inches is fine for lettuce, herbs, and shallow-rooted greens. 10–12 inches works for most vegetables like tomatoes, peppers, and beans. 12–18 inches is ideal for carrots, parsnips, and deep-rooted crops. If the bed sits on native soil, roots can go deeper, so you can sometimes get away with less.
Can I use garden soil from my yard in a raised bed? ▼
You can, but it's risky. Native soil may contain weed seeds, pests, and diseases, and it often compacts poorly in a raised bed. If you do use it, mix it with plenty of compost and aeration amendments like perlite. Many gardeners prefer a sterile or pasteurized topsoil blend for the first fill.
How much does a cubic yard of soil weigh? ▼
A cubic yard of typical garden soil weighs roughly 1,000 to 1,400 pounds (450–640 kg), depending on moisture and composition. Compost is lighter; wet topsoil is heavier. Check with your supplier if weight limits matter for delivery or your raised bed frame.
How do I calculate soil for multiple raised beds? ▼
Enter the dimensions of one bed, then set the "Number of beds" field to however many identical beds you have. Our raised bed soil calculator multiplies the volume automatically. If your beds are different sizes, calculate each size separately and add the totals.