Soil Bulk Density & Compaction & Porosity
Tests compaction
Enter oven-dry soil mass and core ring volume to get bulk density, porosity and a compaction status — so you know whether roots can move freely through the soil.
Soil bulk density
Next: bulk density of 1.53 g/cm³ (moderate) gives roughly 42.34% pore space for air and water.
Mineral soils ideally sit near 1.0–1.3 g/cm³; above ~1.6 roots struggle. Bulk density rises with compaction and falls with organic matter.
Soil bulk density — key facts
- Bulk density
- oven-dry mass ÷ core volume
- Units
- g/cm³
- Healthy range
- ≈ 1.1–1.4 g/cm³
- Roots struggle
- above ~1.6 g/cm³
- Porosity
- (1 − BD ÷ particle density) × 100
- Particle density
- ≈ 2.65 g/cm³
- Sampling
- use a known-volume core ring
- Privacy
- Runs in your browser; nothing uploaded
Read how tightly your soil is packed
Bulk density is one of the most telling numbers in soil health: it captures how much air and pore space the soil holds against how much solid material is crammed in. A well-structured soil is loose and porous, so roots reach down, water soaks in, and air feeds the roots and microbes. A compacted soil — packed by heavy traffic or working it wet — squeezes those pores shut, roots stall at the hardpan, and crops go short of water and oxygen.
This tool gives the core volume, bulk density, porosity and a compaction status from a simple core sample. Take a known-volume ring, oven-dry the core, weigh it, and read whether your soil is open and healthy or dense enough that roots are struggling. Pair it with the Soil Water Holding Capacity, Soil Texture and Soil Organic Carbon tools for a full picture of your soil's physical health.
Spot compaction early
Catch a dense layer before it cuts yields.
Check the root zone
Know if roots can push through the soil.
Estimate porosity
See how much room there is for air and water.
Track improvement
Re-measure after tillage or cover crops.
Frequently Asked Questions
What is soil bulk density?+
Bulk density is the oven-dry mass of soil divided by the total volume it occupies, including the pore spaces — expressed in grams per cubic centimetre (g/cm³). Because it counts the air and water gaps, it's lower than the density of the solid mineral particles and tells you how tightly the soil is packed.
How is bulk density calculated?+
Bulk density = oven-dry soil mass ÷ core volume. Push a ring of known volume into the soil, dry the intact core in an oven, weigh it, and divide. For example a core ring of 100 cm³ holding 135 g of oven-dry soil gives a bulk density of 1.35 g/cm³.
What bulk density means compaction?+
It depends on texture, but as a guide, sandy soils run higher and clays lower. Above roughly 1.6 g/cm³ most roots struggle to push through, water and air movement slow, and yields suffer. Values around 1.1–1.4 g/cm³ usually indicate a healthy, well-structured soil for cropping.
How do I take a core sample?+
Use a steel core ring or soil core sampler of a known internal volume. Drive it into the soil so it fills without compressing the core, trim the ends flush, and remove the intact sample. Dry the whole core at 105 °C until the mass is constant, then weigh — that oven-dry mass is what you enter.
What is porosity and how is it found?+
Porosity is the share of soil volume that is pore space (air and water). It's estimated as porosity % = (1 − bulk density ÷ particle density) × 100, using a particle density of about 2.65 g/cm³ for mineral soils. A bulk density of 1.3 g/cm³ gives roughly 51% porosity — good room for roots, air and water.
Why does particle density default to 2.65?+
Most soil minerals — chiefly quartz, feldspars and clays — average close to 2.65 g/cm³, so it's the standard value for porosity estimates. Soils very high in organic matter or iron oxides differ, but 2.65 is a reliable default for typical agricultural soils and the basis of the porosity formula here.
Why does compaction hurt crops?+
Compacted soil has fewer and smaller pores, so roots can't penetrate, water infiltrates and drains poorly, and oxygen for roots and microbes is limited. The result is shallow rooting, waterlogging or drought stress, and lower yields. Measuring bulk density flags compaction early so you can loosen the soil.
How can I reduce a high bulk density?+
Avoid working or driving on wet soil, control traffic to set lanes, deep-rip or subsoil compacted layers when the soil is dry, add organic matter to build structure, and use cover crops with strong taproots to open the profile. Re-measure after a season to confirm the soil is loosening.
Are the figures precise?+
They're as accurate as your sampling. A clean, uncompressed core of a known volume and a properly oven-dried, accurately weighed sample give reliable bulk density and porosity. Take several cores across a field and average them, since soil varies — bulk density is best read as a trend, not a single spot value.