Soil Calculator
Calculate how much soil, topsoil, or compost you need for garden beds, raised beds, and landscaping projects. See also Mulch Calculator and Gravel Calculator.
Calculation Mode
Cost Estimate (optional)
How Much Soil Do I Need for Raised Beds?
To calculate soil for raised beds, multiply the bed length by width by depth (all in the same unit). A standard 4x8 ft raised bed that is 12 inches deep needs 32 cubic feet (about 1.2 cubic yards) of soil. For multiple beds, multiply by the number of beds. Use a mix of 60% topsoil, 30% compost, and 10% potting mix for optimal growing conditions.
Soil Volume Formula
Volume (cu ft) = Length (ft) x Width (ft) x Depth (in) / 12
Cubic Yards = Volume (cu ft) / 27
Bags (1 cu ft) = Volume (cu ft) rounded up
Tons = Cubic Yards x Soil Density (tons/cu yd)
Raised Beds (multiple):
Total Volume = Bed L x Bed W x Bed D / 12 x Number of Beds
Example Calculation
Raised bed: 4 ft x 8 ft x 12 inches, 2 beds
Volume per bed = 4 x 8 x (12/12) = 32 cu ft
Total = 32 x 2 = 64 cu ft = 2.37 cu yd
Topsoil weight = 2.37 x 1.1 = 2.61 tons
Soil Amendments Guide
Most garden soil benefits from amendments to improve drainage, nutrient content, and structure. Here are common amendments and their purposes:
- Compost (30% of mix): Adds nutrients, improves water retention and drainage.
- Perlite or vermiculite: Improves aeration and drainage in heavy soils.
- Peat moss: Increases water retention in sandy soils (use sustainably sourced).
- Lime: Raises pH for alkaline-loving plants.
- Sulfur: Lowers pH for acid-loving plants like blueberries.
- Sand: Improves drainage in clay soils (use coarse builder sand).
Soil Types Reference
| Soil Type | Density (tons/cu yd) | Lbs per Cu Ft | Best Use | Notes |
|---|---|---|---|---|
| Topsoil | 1.1 | 80 | Lawns, general landscaping | Screened for debris |
| Garden Soil | 1.0 | 75 | Flower beds, gardens | Enriched with compost |
| Potting Mix | 0.5 | 35 | Containers, raised beds | Lightweight, well-draining |
| Compost | 0.6 | 45 | Amendment, top dressing | Rich in nutrients |
| Fill Dirt | 1.3 | 95 | Grading, filling holes | No organic matter |
| Clay Soil | 1.2 | 90 | Structural fill | Poor drainage |
| Sandy Loam | 1.1 | 80 | Gardens, lawns | Good drainage |
Frequently Asked Questions
How much soil do I need for a 4x8 raised bed?
A 4x8 ft raised bed at 12 inches deep needs 32 cubic feet (1.19 cubic yards) of soil. At 6 inches deep, you need 16 cubic feet (0.59 cubic yards). Most gardeners fill beds 10-12 inches deep for vegetables.
What is the best soil mix for raised beds?
The ideal raised bed mix is 60% topsoil, 30% compost, and 10% perlite or coarse vermiculite. This provides nutrients, good drainage, and proper aeration. Some gardeners use equal parts topsoil, compost, and peat moss.
Should I buy bags or bulk soil?
For projects needing more than 1 cubic yard (27 bags of 1 cu ft), bulk delivery is more economical. Bulk soil costs $25-$50 per cubic yard delivered, while 27 bags at $5-$8 each costs $135-$216 for the same volume.
Does soil settle after filling raised beds?
Yes, soil settles 10-20% after watering and over the first growing season. Fill beds slightly above the rim initially, or plan to top off with compost in the fall. Settling is more pronounced with lighter mixes.
Can I reuse old potting soil?
Yes, old potting soil can be refreshed by adding 25-50% new compost and a balanced fertilizer. Remove old roots and debris first. Do not reuse soil from plants that had diseases. Refresh annually for container gardens.
How deep should topsoil be for a new lawn?
New lawns need 4-6 inches of quality topsoil for healthy grass establishment. For overseeding existing lawns, add 1-2 inches of topsoil or compost. Ensure the topsoil is free of weed seeds and debris.
What is the difference between topsoil and garden soil?
Topsoil is the natural upper layer of earth, screened for rocks and debris. Garden soil is topsoil enriched with compost, peat moss, and other amendments for better plant growth. Garden soil costs more but provides better nutrition.