Soil Calculator
Soil Calculator: How Much Topsoil, Fill Dirt, or Garden Soil Do You Need?
Whether you’re filling a raised bed, top-dressing a lawn, leveling a yard, or starting a new garden, the first question is always the same: how much soil do I need? Get the estimate wrong and you’re either making a second delivery run or shoveling excess dirt back into the pile. This guide walks through the soil calculation formula, covers topsoil, fill dirt, compost, and potting soil, and gives you ready-to-use reference tables for every common project.
How to Calculate Soil Volume: The Formula
The dirt calculator formula is the same regardless of what material you’re working with — topsoil, compost, fill dirt, garden soil, or potting mix.
Step 1 — Measure the area in feet
Area (sq ft) = Length × Width
Step 2 — Convert depth to feet
Depth (ft) = Depth (inches) ÷ 12
Step 3 — Calculate volume in cubic feet
Volume (cu ft) = Area × Depth (ft)
Step 4 — Convert to cubic yards
Cubic Yards = Volume (cu ft) ÷ 27
Step 5 — Add 10% for settling and waste
Order Amount = Cubic Yards × 1.10
Worked Example: Garden Bed
A raised garden bed 8 ft × 4 ft, filled to 12 inches deep:
- Area: 8 × 4 = 32 sq ft
- Depth: 12 ÷ 12 = 1 ft
- Volume: 32 × 1 = 32 cu ft
- Cubic yards: 32 ÷ 27 = 1.19 cu yd
- With 10% buffer: 1.3 cu yd → order 1.5 cu yd
Our soil calculator does all five steps instantly — enter dimensions in any unit (inches, feet, centimetres, metres) and get output in cubic feet, cubic yards, or litres.
Topsoil Calculator: Coverage by Depth
One cubic yard of soil covers approximately 324 square feet at a depth of one inch, or about 100 square feet at a depth of three inches.
| Depth | 1 Cubic Yard Covers | 1 Cubic Foot Covers |
|---|---|---|
| 1 inch | 324 sq ft | 12 sq ft |
| 2 inches | 162 sq ft | 6 sq ft |
| 3 inches | 108 sq ft | 4 sq ft |
| 4 inches | 81 sq ft | 3 sq ft |
| 6 inches | 54 sq ft | 2 sq ft |
| 8 inches | 40.5 sq ft | 1.5 sq ft |
| 12 inches | 27 sq ft | 1 sq ft |
Cubic Yards Needed by Area and Depth
| Area (sq ft) | 2″ depth | 3″ depth | 4″ depth | 6″ depth | 12″ depth |
|---|---|---|---|---|---|
| 100 sq ft | 0.62 | 0.93 | 1.23 | 1.85 | 3.7 |
| 200 sq ft | 1.23 | 1.85 | 2.47 | 3.70 | 7.4 |
| 500 sq ft | 3.09 | 4.63 | 6.17 | 9.26 | 18.5 |
| 1,000 sq ft | 6.17 | 9.26 | 12.35 | 18.52 | 37.0 |
| 2,000 sq ft | 12.35 | 18.52 | 24.69 | 37.04 | 74.1 |
Raised Bed Soil Calculator
For raised garden beds, you’re filling the entire depth of the box — not just topdressing. Typical raised beds are 6–12 inches deep, with 12 inches being the minimum for most vegetables.
Soil Volume = Length × Width × Depth (all in feet)
| Raised Bed Size | 6″ deep | 8″ deep | 12″ deep |
|---|---|---|---|
| 2×4 ft | 0.15 cu yd | 0.20 cu yd | 0.30 cu yd |
| 4×4 ft | 0.30 cu yd | 0.40 cu yd | 0.59 cu yd |
| 4×8 ft | 0.59 cu yd | 0.79 cu yd | 1.19 cu yd |
| 4×12 ft | 0.89 cu yd | 1.19 cu yd | 1.78 cu yd |
| 6×8 ft | 0.89 cu yd | 1.19 cu yd | 1.78 cu yd |
| 4×16 ft | 1.19 cu yd | 1.58 cu yd | 2.37 cu yd |
Add 10–15% to each figure for settling — soil compresses after watering.
What Is the 70/30 Rule in Gardening?
The 70/30 rule refers to the ideal soil mix ratio for raised garden beds: 70% topsoil or garden soil + 30% compost or organic matter. The topsoil provides structure and weight while the compost adds nutrients, improves drainage, and supports microbial life. Some raised bed gardeners use a 60/30/10 mix: 60% topsoil, 30% compost, 10% perlite or coarse sand for aeration. Miracle-Gro’s potting mix and similar bagged products are often pre-blended for containers but may need amendment for large raised beds.
Topsoil Weight: Tons to Cubic Yards
Suppliers sometimes quote topsoil by the ton. Here’s how to convert:
One cubic yard of dirt weighs between 1.05 and 1.75 tons depending on the soil composition and water content. Most fill dirt has a density of about 90 pounds per cubic foot, which equals approximately 1.215 tons per cubic yard.
| Soil Type | Weight Per Cubic Yard |
|---|---|
| Dry topsoil | ~1,100 lbs (0.55 tons) |
| Moist topsoil | ~1,800–2,400 lbs (0.9–1.2 tons) |
| Fill dirt (average) | ~2,430 lbs (1.215 tons) |
| Clay-heavy soil | ~2,700–3,000 lbs (1.35–1.5 tons) |
| Sandy soil | ~2,200–2,600 lbs (1.1–1.3 tons) |
| Compost (dry) | ~800–1,000 lbs (0.4–0.5 tons) |
To convert cubic yards to tons: Cubic yards × 1.2 (average)
To convert tons to cubic yards: Tons ÷ 1.2 (average)
Bags of Soil Calculator: How Many Bags Do You Need?
For smaller projects, bagged topsoil or potting mix is more practical than bulk delivery. Standard bag sizes in the US:
| Bag Size | Volume | Coverage at 2″ | Coverage at 3″ |
|---|---|---|---|
| 1 cu ft bag | 1 cu ft = 7.48 L | ~6 sq ft | ~4 sq ft |
| 1.5 cu ft bag | 1.5 cu ft = 11.2 L | ~9 sq ft | ~6 sq ft |
| 40 lb bag topsoil | ~0.75 cu ft = 5.6 L | ~4.5 sq ft | ~3 sq ft |
| 50 L bag (metric) | ~1.77 cu ft | ~10.6 sq ft | ~7 sq ft |
Bags needed = Total Volume (cu ft) ÷ Bag Volume (cu ft)
For a 4×8 raised bed at 12 inches deep (32 cu ft):
32 ÷ 1.5 = 21.3 → order 22 bags of 1.5 cu ft potting mix
Bagged topsoil costs $3 to $7 per bag. To fill just one cubic yard, you would need to purchase 36 forty-pound bags. For anything more than 3–4 cubic yards, bulk delivery is almost always cheaper.
Topsoil Cost Calculator: Price Reference (2025–2026)
Topsoil costs between $2 and $5 per bag or around $10 to $50 per cubic yard in bulk.
| Soil Type | Price Per Cu Yd (Bulk) | Price Per Bag | Best Use |
|---|---|---|---|
| Fill dirt (unscreened) | $5 – $18 | — | Leveling, backfill |
| Fill dirt (screened) | $12 – $25 | — | Smoothing, landscaping |
| Standard topsoil | $12 – $30 | $3 – $5 | Lawns, general gardens |
| Screened loam | $17 – $30 | $3 – $6 | Lawns, flower beds |
| Garden soil blend | $20 – $40 | $4 – $7 | Raised beds, vegetables |
| Black dirt / super loam | $25 – $50 | $5 – $8 | Premium lawns, gardens |
| Organic compost | $20 – $45 | $4 – $8 | Amendments, raised beds |
| Potting mix (container) | $35 – $80 | $5 – $12 | Containers, raised beds |
Delivery fees for topsoil and fill dirt range from $50 to $150 per trip for up to 15 cubic yards. Some companies include delivery in their pricing; others charge separately.
Topsoil Cost by Project Size
| Project | Volume Needed | Bulk Cost (mid-range) |
|---|---|---|
| Small garden bed (4×8, 6″) | ~0.6 cu yd | $12 – $30 |
| Raised bed (4×8, 12″) | ~1.2 cu yd | $24 – $60 |
| Top-dress lawn (1,000 sq ft, 2″) | ~6.2 cu yd | $124 – $310 |
| New lawn (1,000 sq ft, 6″) | ~18.5 cu yd | $370 – $925 |
| Large garden (20×30, 8″) | ~18.5 cu yd | $370 – $925 |
| Full yard fill (5,000 sq ft, 4″) | ~62 cu yd | $1,240 – $3,100 |
Top Dressing Calculator for Lawns
Top dressing a lawn uses a thin layer of compost or screened topsoil — typically 1/4 to 1/2 inch — to improve soil without smothering existing grass.
Top Dressing Formula:
Volume = Area (sq ft) × Depth (in inches) ÷ 324
At 1/4 inch depth, 1 cubic yard covers 1,296 sq ft.
| Lawn Area | 1/4 inch | 1/2 inch | 1 inch |
|---|---|---|---|
| 500 sq ft | 0.39 cu yd | 0.77 cu yd | 1.54 cu yd |
| 1,000 sq ft | 0.77 cu yd | 1.54 cu yd | 3.09 cu yd |
| 2,500 sq ft | 1.93 cu yd | 3.86 cu yd | 7.72 cu yd |
| 5,000 sq ft | 3.86 cu yd | 7.72 cu yd | 15.43 cu yd |
Recommended Topsoil Depths by Project
Topsoil should be 4 to 6 inches deep when planting a new lawn and at least 8 inches deep when filling a garden bed.
| Project | Recommended Depth |
|---|---|
| Top dressing existing lawn | 1/4 – 1/2 inch |
| New lawn from seed | 4 – 6 inches |
| Flower bed | 6 – 8 inches |
| Vegetable garden | 8 – 12 inches |
| Raised bed (shallow roots) | 6 – 8 inches |
| Raised bed (deep roots) | 12 – 18 inches |
| Leveling holes and ruts | 2 – 4 inches |
| Tree planting | 12 – 18 inches |
Dirt Removal and Excavation Calculator
If you’re excavating before filling, you also need to know how much dirt you’re removing. The formula is identical:
Excavation Volume = Length × Width × Depth ÷ 27 (cubic yards)
Dirt removal costs $150–$400 per truckload (10–14 cu yd capacity), or $50–$150 per cubic yard depending on location and accessibility. Use the soil removal calculator to estimate disposal costs alongside your fill dirt needs.
Frequently Asked Questions
How Do I Work Out How Many Litres of Soil I Need?
Calculate your volume in cubic feet first: Length (ft) × Width (ft) × Depth (ft) = cubic feet. Then multiply by 28.3168 to convert to litres. Alternatively, measure in metres and multiply: Length × Width × Depth (all in metres) = cubic metres × 1,000 = litres.
For a 1.2 m × 2.4 m raised bed at 0.3 m (30 cm) deep:
1.2 × 2.4 × 0.3 = 0.864 m³ × 1,000 = 864 litres
How Many 25L Bags of Soil Are in a Cubic Yard?
One cubic yard = 27 cubic feet = 764.5 litres. Divided by 25 litres per bag = 30.6 bags. Round up and order 31 bags of 25L soil to fill one cubic yard. At typical bag prices of £3–£6, that’s £90–£185 per cubic yard — significantly more expensive than bulk delivery.
What Area Will 500 Litres of Topsoil Cover?
500 litres = 0.5 m³ = 17.66 cu ft.
- At 2 inches (5 cm) depth: 0.5 ÷ 0.05 = 10 m² (107 sq ft)
- At 4 inches (10 cm) depth: 0.5 ÷ 0.10 = 5 m² (54 sq ft)
- At 8 inches (20 cm) depth: 0.5 ÷ 0.20 = 2.5 m² (27 sq ft)
How Many Litres of Soil Are in a 5-Gallon Bucket?
A standard 5-gallon bucket holds approximately 18.9 litres. In practical terms, filled with potting soil it holds roughly 5–6 litres less once compacted, so effective soil capacity is around 13–15 litres. For planning purposes, use 19 litres (5 US gallons = 18.93 L) as the nominal volume.
Can I Estimate Soil Volume Without a Calculator?
Yes. The mental math shortcut: Cubic yards ≈ (Square feet × Depth in inches) ÷ 324. For example, 500 sq ft at 4 inches: (500 × 4) ÷ 324 = 2,000 ÷ 324 = 6.17 cubic yards. This works because one cubic yard at 1-inch depth covers exactly 324 square feet. No calculator needed — just multiply area by depth and divide by 324.
What Is the 70/30 Rule in Gardening?
The 70/30 rule recommends filling raised garden beds with 70% high-quality topsoil or garden soil and 30% compost or organic matter. This ratio creates a growing medium with the right balance of structure, drainage, moisture retention, and nutrients. For containers and intensively planted raised beds, some gardeners use an alternative: 60% topsoil + 30% compost + 10% perlite for additional aeration and drainage.