Soil Calculator
Planning a garden bed, building raised vegetable planters, or leveling your lawn? Our free Soil Calculator computes the exact soil volume in cubic yards, cubic feet, or cubic meters. Factoring in bed shape, depth, soil mix density, and settling compaction, you will know precisely whether to buy retail bags or order bulk truckload delivery.
Project Inputs
Enter your measurements to calculate exact materials
Enter measurements above to view calculation results.
Step-by-Step Calculation Example
Scenario: Filling a 12 ft long by 6 ft wide raised garden bed with an 8-inch depth of premium garden soil blend and a 10% settling allowance.
Calculate Surface Area: 12 ft × 6 ft = 72 sq ft.
Convert Depth to Feet: 8 inches ÷ 12 = 0.667 ft.
Compute Net Volume: 72 sq ft × 0.667 ft = 48 cubic feet.
Add 10% Settling & Compaction Buffer: 48 cu ft × 1.10 = 52.8 cubic feet.
Convert to Cubic Yards: 52.8 cu ft ÷ 27 = 1.96 cubic yards.
Determine Retail Bags: 52.8 cu ft ÷ 1.5 cu ft per bag = 36 bags (1.5 cu ft size) or 27 bags (2.0 cu ft size).
Soil Volume & Weight Formula
Volume = Surface Area × Depth × (1 + Settling Buffer %) Surface area is calculated according to the selected geometry (Length × Width for rectangles, π × Radius² for circular beds, or 0.5 × Base × Height for triangular beds). Multiplying area by soil depth yields the geometric cubic volume. A settling buffer (default 10%) is added because loose organic soil naturally settles and compacts after watering.
Formula Variables
Calculation Assumptions
- Standard screened topsoil weighs approximately 100 lb per cubic foot (1.35 tonnes per cubic meter).
- Premium garden soil blended with compost weighs approximately 85 lb per cubic foot (1.15 tonnes per cubic meter).
- Lightweight raised bed soil / peat mixes weigh roughly 70 lb per cubic foot (0.95 tonnes per cubic meter).
- One cubic yard equals 27 cubic feet (or approximately 27 1-cu-ft bags / 13.5 2-cu-ft bags / 18 1.5-cu-ft bags).
- Freshly unbagged soil compacts by 8% to 15% after the first few deep waterings.
Frequently Asked Questions
Common homeowner and DIY questionsSoil Calculator
How much soil do I need for my garden or raised bed?
To calculate soil requirements, multiply the bed length (in feet) by width (in feet) by depth (in feet). For example, a 4x8 ft raised bed that is 1 ft deep requires 32 cubic feet of soil. Adding a 10% settling buffer brings the total to 35.2 cubic feet, or approximately 1.30 cubic yards.
How deep should soil be for vegetables and flowers?
Most vegetables (tomatoes, peppers, carrots, squash) require 8 to 12 inches of soil depth for robust root development. Shallow-rooted crops like lettuce and radishes thrive in 6 inches, while deep-rooted perennials and root vegetables benefit from 12 to 18 inches.
How many bags of soil equal one cubic yard?
One cubic yard equals 27 cubic feet. Therefore, 1 cubic yard equals 27 bags of 1.0-cu-ft soil, 18 bags of 1.5-cu-ft soil, or 13.5 (14 rounded up) bags of 2.0-cu-ft soil.
What is the difference between topsoil, garden soil, and potting mix?
Topsoil is dense, natural screened surface soil ideal for grading and filling deep holes. Garden soil is topsoil enriched with organic compost and nutrients for in-ground and raised beds. Potting mix is a soilless blend of peat moss, perlite, and bark engineered for superior drainage in containers and pots.
Why does soil settle and why do I need a compaction buffer?
Fresh bagged or bulk soil is fluffed with air pockets during processing. When watered, gravity and moisture collapse these microscopic voids, causing the soil level to drop by 8% to 15%. Adding a 10% buffer ensures your planter beds remain full to the desired rim height.
How much soil is needed for lawn top dressing?
For lawn top dressing, apply a 1/4-inch to 1/2-inch layer of finely screened compost or topsoil. Over a 1,000 sq ft lawn, a 1/4-inch layer requires approximately 0.77 cubic yards (21 cu ft) of material.
Is it cheaper to buy bagged soil or bulk truckload delivery?
For projects under 1 to 1.5 cubic yards (under 25 to 40 bags), retail bagged soil is usually easier and more convenient to transport. For larger projects requiring 2 or more cubic yards, bulk truckload delivery from a local landscape yard typically saves 40% to 60% compared to bagged prices.
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