Soil Calculator
Calculate how much soil you need for raised beds, gardens, and landscaping projects. Get volume in cubic yards and bags needed.
Soil Calculation Formulas
Rectangular Bed
Circular Bed
Bags Needed
Weight Estimate
Bed Shape
Soil Type
Recommended Depths
Calculating Soil for Your Garden
Whether you're filling raised beds, starting a new garden, or improving existing soil, knowing exactly how much you need saves money and trips to the store. Our soil calculator helps you determine the precise amount of topsoil, garden soil, potting mix, or compost for any project.
Soil is heavy and expensive to transport, so accurate calculations are essential. Running short means delays and additional delivery fees; over-ordering wastes money and leaves you with piles of excess soil.
Multiple Shapes
Calculate for rectangular, circular, and triangular beds.
Soil Types
Different weight calculations for topsoil, garden soil, and mixes.
Cost Comparison
Compare bagged vs. bulk pricing for best value.
Weight Estimates
Know how much your soil will weigh for transport planning.
Types of Soil and Their Uses
Different projects require different soil types. Using the right soil ensures healthy plant growth and successful gardening outcomes.
Topsoil
The top 4-8 inches of natural soil, containing organic matter and nutrients. Best for: filling large areas, lawn establishment, general landscaping. Not ideal for containers or raised beds without amendments.
Garden Soil
Topsoil enriched with compost and organic matter. Designed for in-ground planting. Better drainage and nutrients than plain topsoil. Use for: garden beds, borders, tree planting holes.
Raised Bed Mix
Specially formulated blend—typically 60% topsoil, 30% compost, 10% perlite or vermiculite. Lightweight, well-draining, nutrient-rich. Perfect for raised beds and elevated planters.
Potting Mix
Lightweight, soilless mix of peat moss, perlite, vermiculite, and bark. Excellent drainage for containers. Not for in-ground planting—it's too light and dries out quickly in open beds.
Compost
Decomposed organic matter—the ultimate soil amendment. Mix into existing soil to improve structure, drainage, and nutrients. Usually added at 2-4 inches and tilled in. Also works as mulch.
Fill Dirt
Subsoil with no organic content. Used for leveling, filling holes, and creating grades. Not for planting—nothing grows well in fill dirt. Cover with topsoil for any planting areas.
Soil Depth Guidelines
Different plants have different root zone requirements. Providing adequate depth ensures healthy root development and productive plants.
| Plant Type | Minimum Depth | Ideal Depth | Notes |
|---|---|---|---|
| Lawn/Grass | 4" | 6-8" | Over prepared subsoil |
| Annual flowers | 6" | 8-10" | Shallow roots |
| Herbs | 6" | 8-12" | Most herbs have shallow roots |
| Leafy vegetables | 6" | 8-12" | Lettuce, spinach, kale |
| Tomatoes, peppers | 12" | 18-24" | Deep root systems |
| Root vegetables | 12" | 18-24" | Carrots, potatoes, beets |
| Perennials | 12" | 18" | Varies by species |
| Shrubs | 18" | 24" | Native soil below OK |
| Trees | 24" | 36" | Width matters more than depth |
Raised Bed Soil Guide
Raised beds are increasingly popular for vegetable gardening, and filling them correctly is crucial for success.
Standard Raised Bed Formula
For a 4x8 ft bed at 12" deep: (4 × 8 × 1) ÷ 27 = 1.2 cubic yards. Add 20% for settling. Use raised bed mix or create your own: 60% topsoil + 30% compost + 10% perlite.
Money-Saving Tip
For deep beds (18"+), fill the bottom third with logs, branches, straw, or cardboard (hugelkultur method). This reduces soil needed and creates long-term fertility as materials decompose.
Settling Allowance
New soil settles 10-20% in the first year. Fill beds slightly higher than desired, or plan to add more soil after the first growing season.
Annual Maintenance
Add 1-2 inches of compost annually to maintain soil level and fertility. This replaces nutrients removed by harvesting and compensates for ongoing settling.
Bagged vs. Bulk Soil
The choice between bagged and bulk soil depends on project size, access, and budget.
When to Buy Bags
Best for: small projects (under 1 cubic yard), container gardening, limited access areas, specific soil types. More expensive but convenient. A cubic yard equals about 27 one-cubic-foot bags.
When to Buy Bulk
Much more economical for large projects (1+ cubic yards). Bulk soil costs $25-$60 per cubic yard vs. $7-$15 per cubic foot bagged. Requires delivery access and a place to dump.
Cost Comparison Example
4x8 ft raised bed (12" deep) needs ~1.2 cubic yards. Bagged (32 bags @ $5): ~$160. Bulk (1.5 yards delivered): ~$75-$100. The savings grow with larger projects.
Quality Considerations
Bulk soil quality varies widely. Ask about the source and composition. Visit the supplier if possible. Premium bagged mixes are often higher quality than budget bulk soil.
Soil Improvement Tips
Even the best soil benefits from ongoing improvement. Building healthy soil is a continuous process.
Test Your Soil
Before adding amendments, get a soil test from your local extension office ($15-$30). Know your pH, nutrient levels, and organic matter content. This prevents over-amending and guides purchases.
Improve Clay Soil
Add 2-4 inches of compost and work it in deeply. Gypsum helps break up clay. Avoid tilling when wet. Plant cover crops in off-seasons. Improvement takes 2-3 years of consistent effort.
Improve Sandy Soil
Add compost generously—it increases water and nutrient retention. Mulch heavily to prevent moisture loss. Sandy soil improves faster than clay. Annual compost additions are key.
Build Organic Matter
Healthy garden soil should contain 5-10% organic matter. Add compost, aged manure, leaf mold, or other organics. Mulch with organic materials that decompose into the soil.
Common Mistakes
Don't add sand to clay (creates concrete-like soil). Don't use fresh manure near plants. Don't add lime without a soil test. Don't work soil when wet. Don't skip the compost.
Frequently Asked Questions
How much does a cubic yard of soil weigh?
It depends on the type: Topsoil weighs about 2,000-2,200 lbs per cubic yard. Garden soil is slightly lighter at 1,800-2,000 lbs. Potting mix is much lighter at 600-800 lbs. Wet soil can weigh 25-50% more than dry.
How many bags of soil fill a 4x8 raised bed?
At 12" deep: about 32 one-cubic-foot bags, 16 two-cubic-foot bags, or 1.2 cubic yards bulk. At 18" deep: about 48 one-cubic-foot bags or 1.8 cubic yards. Our calculator gives exact amounts for your dimensions.
Should I use garden soil or potting mix in raised beds?
Use a raised bed mix or garden soil blend—not potting mix alone. Potting mix is too light for raised beds (dries out quickly, blows away). Garden soil provides weight and nutrients. Mix potting elements (perlite) with garden soil for best results.
How do I fill a very deep raised bed affordably?
Use the hugelkultur method: fill the bottom 1/3 with logs, branches, leaves, straw, or cardboard. Top with cheaper fill soil or subsoil for the middle 1/3. Use quality garden soil for the top 12 inches where roots grow. This cuts costs 30-50%.
Can I use native soil in raised beds?
You can mix native soil with amendments if it's reasonably good quality. A 50/50 mix of native soil and compost works well. Don't use pure native soil—it often drains poorly in raised beds. Never use soil from unknown sources (may contain chemicals or diseases).
How much soil settling should I expect?
New soil typically settles 10-20% in the first year, more for loose mixes. Fill beds about 2 inches higher than desired to compensate. After the first year, annual settling is minimal—just top up with compost each spring.
What's the best soil mix for vegetables?
The classic raised bed mix: 60% topsoil, 30% compost, 10% perlite or coarse sand. Some gardeners prefer: 1/3 topsoil, 1/3 compost, 1/3 peat moss or coco coir. Both provide good drainage and nutrients. Add slow-release fertilizer at planting time.
How often should I replace raised bed soil?
You don't need to replace it—properly maintained soil lasts indefinitely. Add 1-2 inches of compost annually. Rotate crops to prevent nutrient depletion and disease. If soil becomes compacted or diseased, remove the top 6 inches and replace with fresh mix.
Pro Tips
- Bookmark this calculator for quick access in the future
- Use the share button to send your results to others
- Try different scenarios to compare outcomes
- Check out our related calculators for more insights
Found this calculator helpful? Share it with others: