Soil Bulk Density Calculator
Optional. Loads the soil USDA maps at a US address to prefill and tailor the result.
How to take the sample
- Drive a ring 3 inches in diameter 3 inches into the soil, keeping the core intact.
- Dig the ring out, trim the core flush with both ends, and seal it in a bag.
- Weigh the bagged moist core, and weigh the empty bag so you can subtract it.
- Find the water content: either dry a weighed subsample and compare, or oven-dry the whole core. At home, microwave the subsample in 4-minute cycles at medium power until the weight stops dropping[1].
- Dry weight = moist weight ÷ (1 + water content); bulk density = dry weight ÷ the ring’s volume.
Bulk, particle and wet density
Bulk density is the mass of a volume of dry soil, and that volume includes the pores as well as the solids. Particle density is the mass of the solids divided by the volume of the solids alone. Kansas State University’s soils lab manual notes that density matters for both plant growth and engineering, and that as soil density rises, porosity falls[2]. The soil porosity calculator turns the two densities into pore space.
Wet (moist) density is the moist mass divided by the volume. Engineers call the oven-dry figure the dry density and get it as wet density ÷ (1 + water content), with the water content as a decimal[3]. That dry density is the bulk density this calculator reports.
Engineers also compact soil in the lab to find the moisture that packs it densest, for fill and foundations[3]; the soil moisture content calculator explains how that test differs from measuring garden soil.
What density restricts roots
USDA-NRCS relates bulk density to root growth by texture. Below the ideal column there is no restriction; above the right column, roots are restricted[1]. Two classes, silt loam and clay loam, appear in two rows because they sit on a boundary between groups.
| Soil texture | Ideal (<) | May affect roots | Restricts roots (>) |
|---|---|---|---|
| sand, loamy sand | 1.60 | 1.63 | 1.80 |
| sandy loam, loam | 1.40 | 1.63 | 1.80 |
| sandy clay loam, clay loam | 1.40 | 1.60 | 1.75 |
| silt, silt loam | 1.40 | 1.60 | 1.75 |
| silt loam, silty clay loam | 1.40 | 1.55 | 1.65 |
| sandy clay, silty clay, clay loam | 1.10 | 1.49 | 1.58 |
| clay (<45% clay) | 1.10 | 1.39 | 1.47 |
Does not apply to red clayey soils and volcanic ash. Source: USDA-NRCS Soil Health Guide.
Typical bulk density by texture
For a reference point, here is the median surface bulk density USDA records for each texture class across its mapped US soils[4]. Field-measured values vary, so compare your result with these rather than treating them as a target.
| Texture class | Median bulk density (g/cm³) |
|---|---|
| sand | 1.54 |
| loamy sand | 1.53 |
| sandy loam | 1.45 |
| loam | 1.37 |
| silt loam | 1.3 |
| silt | 1.25 |
| sandy clay loam | 1.45 |
| clay loam | 1.35 |
| silty clay loam | 1.34 |
| sandy clay | 1.35 |
| silty clay | 1.32 |
| clay | 1.27 |
Worked example
A 3-inch ring driven 3 inches deep holds about 347 cm³ of soil. Say the moist core weighs 550 g net of the bag, and a subsample dries from 50 g to 40 g, so its water content is 0.25. The dry weight is 550 ÷ 1.25 = 440 g, and the bulk density is 440 ÷ 347 = 1.27 g/cm³ (about 79 lb/ft³, calculated[5]). For loam that is below 1.40, so it is ideal for roots[1].
What to do with a high reading
If your reading lands in the restricts column, see how to fix compacted soil, then turn the same reading into pore space with the soil porosity calculator.
How this calculator works
The ring’s volume is π r² × height, computed in centimeters. Water content is (moist − dry) ÷ dry from your subsample, or you can enter the core’s oven-dry weight directly. Dry weight = moist ÷ (1 + water content), and bulk density is that divided by the volume[1]. The verdict reads the NRCS table row for your texture.
Pounds per cubic foot use 1 g/cm³ = 62.428 lb/ft³, calculated from NIST’s conversion factor for pounds per cubic foot[5].
With “Use my soil”, USDA’s mapped value for your address is shown alongside as a reference[4].
Frequently asked questions
What is a good soil bulk density?
It depends on texture. For sandy loam and loam, below 1.40 g/cm³ is ideal and above 1.80 restricts roots; for clay, below 1.10 is ideal and above 1.47 restricts roots[1].
How do I measure bulk density at home?
Drive a 3-inch ring 3 inches into the soil, bag and weigh the core, then dry a subsample (a microwave in 4-minute cycles at medium power works) to find its water content. Dry weight = moist ÷ (1 + water content), and bulk density is that dry weight divided by the ring’s volume[1].
What is the formula for soil density?
Bulk density is the mass of dry soil divided by the volume it fills, pores included; particle density is the mass of the solids divided by the volume of the solids alone[2]. Wet density is the moist mass divided by the volume, and dry density = wet density ÷ (1 + water content)[3].
What bulk density restricts root growth?
On the NRCS table it is anything above the right-hand column for your texture: 1.80 g/cm³ for sand and loam, down to 1.47 for clay[1].
Sources
- USDA NRCS Soil Health Guide, Bulk Density
- Kansas State University, Soils Laboratory Manual, ch. 8: Soil Density (Moorberg and Crouse)
- University of Texas at Arlington, Properties and Behavior of Soil: Online Lab Manual, ch. 6: Compaction Test (Hossain et al., 2021)
- USDA NRCS, Soil Survey Geographic Database (SSURGO), via Soil Data Access
- NIST, Guide for the Use of the International System of Units (SP 811), Appendix B.8: Factors for Units Listed Alphabetically
Marko Visic · MPharm, BSc Physics · Last reviewed November 13, 2026