Garden Soil Volume Calculator
Cubic feet
50.0
Cubic yards
1.85
How it works
Garden beds and containers require precise soil volume estimates to avoid under-ordering (leaving gaps) or over-ordering (wasted cost). The Garden Soil Volume Calculator computes cubic feet and cubic yards needed for rectangular, circular, and L-shaped beds at a specified depth.
**Depth guidelines** Annual vegetables need at least 12 inches of loose, well-draining soil. Perennials and shrubs need 18 to 24 inches. Shallow-rooted plants like lettuce and herbs can thrive in 6 to 8 inches. Most raised beds are built 8 to 12 inches deep to balance root space with material cost.
**Cubic yards conversion** Bulk soil and compost are typically sold by the cubic yard (27 cubic feet). A 4x8 foot bed at 12 inches depth = 32 cubic feet / 27 = 1.18 cubic yards. Always order 5 to 10% overage to account for settling — soil compresses 10 to 20% over the first season as air pockets compress.
**Soil mix recommendations** For raised beds, the classic mix is 1/3 blended compost, 1/3 peat moss or coco coir, 1/3 coarse vermiculite. This mix drains well, holds moisture, and provides nutrients without the compaction risk of native soil.
**Weight considerations** Moist topsoil weighs approximately 100 lbs per cubic foot. A 4x8x1 foot bed holds around 3,200 lbs of wet soil — important for deck planters and rooftop gardens that have structural weight limits.
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Frequently Asked Questions
- Topsoil is native soil from the top 6–12 inches of ground — nutrient content and drainage vary widely by source. It's the cheapest bulk option but may contain weed seeds, clay, or poor drainage. Garden soil (bagged) is topsoil amended with compost and sometimes perlite — better structure but still heavy. Potting mix (or potting soil) is a soilless blend of peat moss, perlite, and compost — designed for containers and raised beds where drainage and aeration matter more than cost. Never use potting mix to fill large in-ground beds (too expensive and unnecessary); never use heavy topsoil in containers (compacts and drowns roots).
- Minimum 12 inches for most annual vegetables (tomatoes, peppers, cucumbers, squash). Root vegetables (carrots, parsnips, beets) need 18 inches minimum, especially for long carrot varieties. If building over clay soil or compacted ground, 12 inches is sufficient because roots will penetrate into the native soil below. If building over concrete, gravel, or hardscape, go to 18–24 inches to ensure adequate depth for root development and water buffering. Deeper beds hold moisture longer and maintain more stable temperatures — beneficial in hot climates. Cost-benefit typically makes 12 inches the standard for most gardens.
- Dry topsoil: approximately 2,000 lbs (1 ton) per cubic yard. Moist topsoil: 2,200–2,700 lbs per cubic yard. Wet soil or clay: up to 3,000 lbs per cubic yard. Compost (mature): approximately 1,000–1,200 lbs per cubic yard. Potting mix: 400–600 lbs per cubic yard (lightest, due to perlite and peat). These weights matter for deck and rooftop gardens where structural loading is a concern — always check load limits before installing heavy raised beds on structures. A standard 4×8-foot raised bed filled 12 inches deep with moist topsoil weighs approximately 3,600 lbs.
- For raised beds sitting on the ground: you don't need to mix — roots will penetrate into native soil naturally. The raised bed mix provides a superior growing medium for the top 12 inches; native soil below provides additional depth and moisture retention. For in-ground beds amended with compost: till 3–4 inches of compost into the existing soil to a depth of 12 inches. Mixing is essential here — surface-applied compost compacts into a mat rather than improving the whole root zone. For containers and raised beds over hardscape: use only a quality potting mix — never mix native soil into containers, as it compacts severely and impedes drainage.