Raised Bed Soil Calculator
Find out exactly how much soil your raised garden beds need, in cubic feet, cubic yards and bags, with a breakdown for your soil mix.
Bed Size
Keep beds 4 ft wide or less so you can reach the middle.
Usually the bed height minus about 1 in.
Settling Allowance
Soil Mix
Your Soil Estimate Will Appear Here
Enter your bed size and fill depth, then click “Calculate Soil Needed.”
Soil & Raised Bed Supplies
Hand-picked products to help you get the best results on your project.
Raised bed mix
Raised Bed Soil Mix
- ✓Ready to plant
- ✓Blended for containers and beds
- ✓No mixing needed
Compost
Organic Compost
- ✓Feeds the soil
- ✓Improves drainage and moisture
- ✓Top up beds every season
Metal raised bed
Galvanized Metal Raised Garden Bed, 8 x 4 x 1 ft
- ✓Long-lasting steel
- ✓Easy to assemble
- ✓Common 4 x 8 size
Coco coir
Coco Coir Brick
- ✓Holds moisture
- ✓Peat-free alternative
- ✓Expands with water
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How the Calculation Works
1. Volume
Length × width × fill depth (converted to feet) gives cubic feet per bed, multiplied by the number of beds.
2. Settling
Fresh soil settles after watering. We add 10% by default so the bed stays full after the first few weeks.
3. Bags or Bulk
Divide by the bag size (1, 1.5 or 2 cu ft) and round up, or divide by 27 for cubic yards of bulk soil.
Soil for Common Raised Bed Sizes
| Bed (12 in deep) | Cubic feet | Cubic yards | 2 cu ft bags |
|---|---|---|---|
| 4' × 4' | 17.6 | 0.65 | 9 |
| 3' × 6' | 19.8 | 0.73 | 10 |
| 4' × 8' | 35.2 | 1.3 | 18 |
| 4' × 12' | 52.8 | 1.96 | 27 |
| 4' × 8' (18 in deep) | 52.8 | 1.96 | 27 |
All figures include a 10% settling allowance.
Filling Tips
Tall beds don’t need to be all soil. For beds deeper than about 18 in, many gardeners fill the bottom with logs, branches and leaves to save on soil. Most vegetables root in the top 12 in.
Water as you fill. Add soil in layers and water each one. It shows you how much the mix settles before you plant.
Top up every season. Beds lose a little volume each year as organic matter breaks down; 1–2 in of compost each spring keeps them full and fertile.
Mulching paths between beds? Use the mulch calculator.
Frequently Asked Questions
A 4 x 8 ft bed filled 12 inches deep holds 32 cubic feet of soil. Adding 10% for settling brings it to about 35 cubic feet, which is roughly 1.3 cubic yards or 18 bags of 2 cubic feet.
Multiply length x width x depth (all in feet) to get cubic feet, add about 10% for settling, then divide by the bag size. For 2 cubic foot bags, divide by 2; for 1.5 cubic foot bags, divide by 1.5. Always round up.
A simple, reliable mix is about 60% screened topsoil and 40% compost. Another popular option is equal parts compost, peat moss or coco coir, and coarse vermiculite. Bagged raised bed mixes work well for small beds and save mixing.
For a bed or two, bags are simplest. Once you need more than about 2 cubic yards (roughly 27 bags of 2 cubic feet), bulk soil delivered by the yard is usually cheaper, even with a delivery fee. Prices vary by area, so compare local quotes.
Fresh soil and compost contain a lot of air. After watering and a few weeks of rain, the mix compacts and can drop several inches. That's why we add 10% by default and why it helps to top up beds with compost each season.