How the Soil Converter Works
The Soil Converter divides soil mass by soil bulk density. The default 1.25 kg/L fits loose garden topsoil.
Pick the soil type
Topsoil, potting mix, clay, loam and fill dirt differ in density.
Allow for moisture
Wet soil weighs up to 30% more than dry soil; use the moist value for delivered loads.
Enter the mass
Type the soil weight in kilograms.
Read the volume
Use the liters to fill raised beds, planters and holes.
Soil Converter Formula
The soil formula is V = m ÷ ρb. Soil porosity equals 1 − ρb ÷ 2.65.
- ρb
- Soil bulk density, kg/L
- ρs
- Soil particle density, about 2.65 kg/L for mineral soil
Worked Examples
- Bulk bag of topsoil: 1,000 kg ÷ 1.25 = 800 L (0.8 m³).
- Raised bed 2.4 × 1.2 × 0.3 m: 0.864 m³ × 1.25 = 1.08 t of topsoil.
- Porosity of loam at 1.30 kg/L: 1 − 1.30 ÷ 2.65 = 51% pore space.
Soil Converter Conversion Table
1 tonne of loose topsoil fills 0.8 m³ (1.05 yd³). The table lists 8 soil types with porosity.
| Soil Type | Bulk Density (kg/L) | m³ per Tonne | yd³ per Tonne | Liters per 25 kg Bag | Porosity |
|---|---|---|---|---|---|
| Potting mix (peat-based) | 0.40 | 2.500 | 3.270 | 62.5 | n/a (organic) |
| Loose garden topsoil | 1.25 | 0.800 | 1.046 | 20.0 | 53% |
| Loam (field) | 1.30 | 0.769 | 1.006 | 19.2 | 51% |
| Silt loam | 1.35 | 0.741 | 0.969 | 18.5 | 49% |
| Clay (field) | 1.20 | 0.833 | 1.090 | 20.8 | 55% |
| Sandy soil (field) | 1.55 | 0.645 | 0.844 | 16.1 | 42% |
| Fill dirt (moist) | 1.60 | 0.625 | 0.817 | 15.6 | 40% |
| Compacted subsoil | 1.80 | 0.556 | 0.727 | 13.9 | 32% |
What is a Soil Converter?
A Soil Converter is a calculator that converts soil weight into volume using soil bulk density.
Soil bulk density is the dry mass of soil per unit volume, pores included. Healthy loam sits at 1.1–1.4 kg/L, with about half the volume as pore space for air and water.
USDA Natural Resources Conservation Service (NRCS) guidance rates root growth as restricted above 1.80 kg/L in sandy soils and above 1.47 kg/L in clay soils.
What are the Uses of a Soil Converter?
There are 4 main uses of a Soil Converter.
Raised bed filling
Gardeners convert bed volume into bag counts.
Earthworks
Contractors convert excavated tonnes into truckloads.
Soil carbon studies
Researchers convert carbon % into tonnes per hectare.
Planter weight
Designers check rooftop and balcony planter loads.