Soil Depth Calculator

Example data table

Soil depth targets by plant type

Soil depth controls rooting volume, oxygen exchange, and water storage. Shallow fills can limit growth, while overly deep fills may waste material. Many vegetables perform well around 20–30 cm of workable soil, lawns often target 8–15 cm, and shrubs benefit from deeper zones when drainage is stable. Use the calculator to match depth to the bed’s footprint.

Compaction and waste allowances

Fresh soil settles after watering, rainfall, and foot traffic. A practical planning approach is to add a compaction allowance (often 5–15%) plus a small waste allowance (typically 2–8%) for uneven spreading and minor spillage. The purchase factor in this calculator multiplies installed volume by (1 + compaction) × (1 + waste) to reduce underbuying.

Unit conversion and quality checks

Mixed units are common on sites, so the tool standardizes everything to square meters and cubic meters before producing liters, cubic feet, and cubic yards. For accuracy, measure internal bed dimensions, avoid guessing curved edges, and recheck values after changing units. If you know area from a plan, select the area option to bypass shape assumptions.

Bulk density and handling estimates

Bulk density varies with texture and moisture. A common planning range for screened topsoil is roughly 1100–1400 kg/m³, while wet or clay-heavy material can be higher. This calculator uses density only to estimate weight for transport and handling. Weight estimates help you decide between bagged soil, bulk delivery, and the number of trips needed.

Example data for quick planning

The table below shows sample inputs and typical outputs using 10% compaction and 5% waste. Replace the dimensions and depth with your real measurements for reliable purchasing quantities.

How do I measure an irregular garden bed?

Break the bed into simple shapes, add areas, then use the “area” option. For curves, measure several widths along the length and use an average width for a practical estimate.

What depth is best for vegetables?

Many vegetables do well with 20–30 cm of workable soil. Deep-rooting crops can benefit from more depth if the base drains well and the soil remains loose.

Why does the calculator add compaction and waste?

Soil settles after watering and handling, and small losses occur during spreading. Allowances reduce the risk of buying short and leaving thin spots that affect plant performance.

How accurate are bag estimates?

Bag counts are rounded up to whole bags and assume labeled volume is close to actual. Moisture and settling can change real yield, so a small buffer is still sensible.

Should I use liters or cubic yards for ordering?

Use liters for bagged products and cubic yards or cubic meters for bulk deliveries. The calculator shows both, so you can compare retailers and delivery minimums easily.

Does bulk density change the volume result?

No. Volume comes from area and depth. Density only estimates weight for transport planning, such as truck capacity, handling effort, and whether a delivery is more practical.

Can I calculate layered fills, like compost plus topsoil?

Yes. Run one calculation per layer using its thickness, then add purchase volumes. Keep separate notes if densities differ, especially when you need realistic weight estimates.