Soil Calculator

This free soil calculator estimates the volume needed for raised beds, circular beds, garden boxes, compost bins, planters, and trapezoidal beds using basic geometric formulas. Enter the shape and dimensions of your space, then calculate using the same formulas applied in our geometry volume calculator. It provides soil volume in cubic feet, yards, or meters for accurate filling and delivery.

What Is Garden Soil?

Garden soil is a blended growth medium composed of mineral particles, organic matter, water, and air in proportions that sustain plant roots. The mineral fraction—sand, silt, and clay—controls drainage and nutrient retention, while composted organics add nitrogen, phosphorus, and beneficial microbes. Ideal loam contains roughly 40 % sand, 40 % silt, and 20 % clay, offering structure and moisture balance. Volume estimation is critical because under-filling raised beds leads to root constriction, whereas over-ordering increases cost and labor.

Garden setup note: Last spring, I built three raised beds for herbs and veggies. I didn’t want to overbuy soil, so I used a soil calculator to work it out. Each bed was 6×3×1.5 ft, which came to 27 cubic feet. For oddly shaped sections, I also checked the volume calculator to make sure I was in the right ballpark.

Common Bed Shapes and Layouts

Six shapes dominate home and market-garden design: rectangular raised beds, round planters, trapezoidal terraces, tiered boxes, circular herb spirals, and octagonal keyhole beds. Each geometry maps to a standard volume formula—prism, cylinder, or composite. Accounting for edging thickness and internal pathways prevents material shortages. A soil volume calculator streamlines these shape conversions and supports rapid bed scaling across large plots.

Measuring Dimensions and Depth

Accurate measurement begins with firming the bed perimeter, then recording inside length, width, and planned soil depth. Depth varies by crop: lettuce thrives in 15 cm, tomatoes need 30 – 45 cm, and root vegetables benefit from 40 cm or more. Builders often round up by 10 % to allow for settlement and minor leveling. Entering these values into a soil calculator produces cubic-foot, cubic-meter, and cubic-yard outputs that match bulk-bag or truck-load quantities.

Loading, Filling, and Compaction

Soil is delivered in 1 m³ super-sacks, 40 lb retail bags, or 10-yard dump-truck loads. Filling starts by loosening native subgrade to improve drainage. Soil is then tipped in layers of roughly 15 cm and lightly raked to eliminate voids. Excessive compaction should be avoided; gentle consolidation under irrigation will naturally settle the surface by about 5 %. Topping off after one week ensures final depth aligns with planting requirements.

Amendment and Long-Term Health

Even bulk soil mixes benefit from annual amendments of compost, aged manure, rock dust, and biochar. These inputs replenish nutrients, buffer pH, and sustain microbial life. Mulching with straw or wood chips controls evaporation and suppresses weeds. Periodic re-measurement using the soil calculator helps gardeners track volume loss through decomposition and harvesting, informing timely top-ups that maintain root-zone depth and maximize yield.