Soil Calculator
Calculate how much soil or compost you need for raised beds and garden areas.
Enter length, width, and depth in feet or meters.
How Garden Soil Volume Is Calculated
Whether filling a raised bed, pot, or garden trench, calculating soil volume prevents both running short and wasting money on excess material.
Volume Formulas:
Rectangular bed: V = Length × Width × Depth
Circular bed: V = π × Radius² × Depth
Worked Examples:
Raised bed (2.4m × 1.2m × 0.3m deep):
- V = 2.4 × 1.2 × 0.3 = 0.864 m³ = 864 liters
Large circular pot (diameter 60cm, depth 40cm):
- Radius = 0.30 m
- V = π × 0.09 × 0.40 = 0.113 m³ = 113 liters
Converting to Bags:
- 50L bags: 864 / 50 = 17.3 → 18 bags
- Always buy 10% extra for settling (soil compacts after watering)
Soil Mix for Raised Beds (Mel’s Mix): A proven formula by Mel Bartholomew for productive raised bed gardening:
- 1/3 blended compost (5+ types mixed)
- 1/3 peat moss or coconut coir
- 1/3 coarse vermiculite
Soil Settling: Freshly filled beds settle 15–25% over the first growing season as organic matter decompresses and microbes break it down. Plan for this by overfilling initially, or top-dress with compost each year.
Soil Weight Reference:
- Potting mix: ~400–500 kg/m³
- Garden soil (loam): ~1,200–1,400 kg/m³
- Saturated clay: ~1,600–1,800 kg/m³
For raised beds and containers, always use lightweight potting mix — not heavy garden soil.