Calculator
Formula Used
Bulk density measures oven dry soil mass per total sample volume.
BD = oven dry soil mass / total soil volume
Core volume = π × radius² × height
Dry mass from wet mass = wet mass / (1 + moisture percent / 100)
Fine earth BD = fine dry mass / fine volume
Porosity % = (1 - bulk density / particle density) × 100
How to Use This Calculator
- Select dry mass or wet mass with moisture.
- Enter the soil mass and choose its unit.
- Select a volume method.
- Enter known volume, core dimensions, or water displacement.
- Add particle density for porosity estimation.
- Enter coarse fragment data when gravel correction is needed.
- Add field area and depth for soil mass estimates.
- Press Calculate, then export CSV or PDF.
Example Data Table
| Sample | Dry Mass g | Volume cm³ | Bulk Density g/cm³ | Particle Density g/cm³ | Porosity % |
|---|---|---|---|---|---|
| Loam Core | 500 | 400 | 1.250 | 2.65 | 52.83 |
| Sandy Core | 620 | 410 | 1.512 | 2.65 | 42.94 |
| Clay Core | 430 | 380 | 1.132 | 2.65 | 57.28 |
Define and Calculate Soil Bulk Density
What Soil Bulk Density Means
Soil bulk density is a chemistry and soil science value. It shows how much dry soil mass fits inside a known total volume. The total volume includes mineral particles, organic matter, water spaces, and air spaces. A low value often means loose soil. A high value often means compacted soil.
Why It Matters
Bulk density helps explain root growth, water flow, aeration, and nutrient movement. It also helps compare field samples. Farmers use it to check compaction. Engineers use it to review soil structure. Laboratory workers use it to standardize samples. The value supports better soil management decisions.
How Samples Are Measured
A common method uses a metal core. The core is pushed into soil without crushing the structure. The soil is trimmed level with the ring. The sample is then dried in an oven. After drying, its mass is measured. The core volume is calculated from its height and diameter.
Moisture and Volume Options
This calculator accepts dry mass directly. It can also estimate dry mass from wet mass and moisture content. Volume can be entered directly. It can be calculated from a cylinder. It can also come from water displacement. These options help with field cores, clods, and prepared samples.
Coarse Fragment Correction
Gravel and stones can change the result. A total density includes the whole sample. A fine earth density removes coarse fragment mass and volume. This correction is useful when the sample has many rock fragments. It gives a better value for the smaller soil fraction.
Porosity and Interpretation
Porosity is estimated from bulk density and particle density. Many mineral soils use 2.65 g/cm³ as a default particle density. Organic soils may need another value. High porosity supports air and water storage. Low porosity may limit roots. Texture also affects interpretation, because sand, loam, and clay have different natural density ranges.
Use in Reports
The calculator gives common unit conversions. It also estimates field dry mass from area and depth. CSV export helps with spreadsheets. PDF export helps with lab records. Always report sampling method, drying condition, units, and any coarse fragment correction.
FAQs
What is soil bulk density?
Soil bulk density is oven dry soil mass divided by total soil volume. The volume includes solids and pores. It is usually reported in g/cm³, Mg/m³, or kg/m³.
Why is oven dry mass used?
Water changes sample mass. Oven drying removes most moisture. That gives a stable dry mass for comparing soil samples from different places or dates.
What is a normal bulk density?
Normal values depend on texture and organic matter. Many mineral soils range from about 1.1 to 1.6 g/cm³. Sandy soils can be higher.
How does compaction affect bulk density?
Compaction pushes particles closer together. It reduces pore space and raises bulk density. High compaction can restrict roots, air movement, and water infiltration.
What particle density should I use?
A common default for mineral soil is 2.65 g/cm³. Use measured particle density when available, especially for organic, volcanic, or unusual soils.
Can wet soil mass be used?
Yes. Enter wet mass and gravimetric moisture percent. The calculator estimates dry mass using wet mass divided by one plus moisture fraction.
Why correct for coarse fragments?
Stones and gravel occupy volume but are not fine soil. Correction helps estimate the density of the fine earth fraction more accurately.
What does high porosity mean?
High porosity means more pore space. It can improve aeration and water storage. Very high values may occur in loose or organic-rich soil.