Porosity and Permeability Calculator
Compute porosity permeability using validated scientific equations. See step-by-step derivations, unit analysis, and reference values.
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Adjust values & calculateResults
35.00%
35.09%
0.5385
0.24%
2.5000e-3 cm/s
1.4094e-6 cm/s
Moderate porosity (sand)
Formula
Porosity n equals the void volume divided by total volume, or equivalently 1 minus the ratio of bulk density to grain density. Void ratio e = n/(1-n). Permeability is estimated using the Hazen formula K = C * d10^2 for clean sands, or the Kozeny-Carman equation which relates permeability to porosity cubed divided by (1-n) squared times grain diameter squared divided by 180.
Last reviewed: December 2025
Worked Examples
Example 1: Sand Sample Porosity and Permeability
Example 2: Clay Soil Porosity Analysis
Background & Theory
The Porosity and Permeability Calculator applies the following established principles and formulas. Earth science calculators draw on a wide range of measurement scales and physical principles that quantify natural phenomena across geological, atmospheric, and hydrological systems. Earthquake magnitude is most precisely described by the Moment Magnitude Scale (Mw), which replaced the original Richter scale for larger events. Mw is calculated as Mw = (2/3) log10(M0) − 10.7, where M0 is the seismic moment in dyne-centimeters. The Richter scale, while still referenced colloquially, is a local magnitude (ML) measurement derived from peak seismograph amplitude at a standard 100 km distance. Wind intensity is classified using the Beaufort Scale, a 13-point empirical scale (0–12) relating wind speed in knots to observable sea and land effects, with Beaufort 12 corresponding to hurricane-force winds above 64 knots. Tropical cyclone intensity is further categorized by the Saffir-Simpson Hurricane Wind Scale, which assigns Categories 1 through 5 based on sustained wind speed, correlating with expected structural damage. Mineral hardness is quantified on the Mohs scale (1–10), comparing scratch resistance relative to reference minerals from talc (1) to diamond (10). Soil composition analysis measures the proportions of sand, silt, and clay by particle size, alongside organic matter content, bulk density, and porosity, which together determine engineering and agricultural suitability. Seismic wave velocity in rock varies by material: P-waves travel at approximately 5–7 km/s in granite and 1.5 km/s in water, while S-waves travel at roughly 60% of P-wave speeds. Atmospheric pressure decreases with altitude according to the barometric formula: P = P0 × exp(−Mgh / RT), where M is molar mass of air, g is gravitational acceleration, h is altitude, R is the universal gas constant, and T is temperature in Kelvin. Standard sea-level pressure is 101,325 Pa. Tidal calculations use harmonic analysis of gravitational forcing by the Moon and Sun, with the principal lunar semidiurnal tidal constituent (M2) having a period of approximately 12.42 hours.
History
The history behind the Porosity and Permeability Calculator traces back through the following developments. The systematic study of Earth's structure and processes spans millennia, but the scientific foundations were laid in the seventeenth century. In 1669, Danish naturalist Nicolas Steno published his principles of stratigraphy, establishing the laws of superposition, original horizontality, and lateral continuity — foundational rules for reading rock layers that remain in use today. Scottish geologist James Hutton introduced the concept of uniformitarianism in 1788, proposing that geological processes observable in the present have operated throughout Earth's history at broadly consistent rates. This idea of deep time challenged prevailing biblical chronologies and set the stage for modern geology. Charles Lyell systematized these ideas in his landmark three-volume work Principles of Geology, published beginning in 1830, which directly influenced Charles Darwin's thinking on biological evolution during the voyage of the Beagle. The nineteenth century saw growing curiosity about continental shapes, but a coherent theory awaited Alfred Wegener, a German meteorologist who proposed continental drift in 1912, arguing that the continents had once formed a supercontinent he called Pangaea. His evidence included matching fossil records and geological formations across the Atlantic, but his mechanism was disputed for decades. The theory gained acceptance in the 1960s when seafloor spreading was confirmed through paleomagnetic studies, and plate tectonics emerged as the unifying framework of modern geoscience. The United States Geological Survey was established by Congress in 1879 to classify public lands and examine the geological structure, mineral resources, and products of the national domain. The twentieth century brought instrumental advances, including the global seismograph network deployed after World War II, initially to monitor nuclear tests, which dramatically improved earthquake detection and characterization. Satellite Earth observation began in earnest with the Landsat program launched in 1972, enabling continuous global monitoring of land use, glacier retreat, and vegetation patterns. Today, GPS networks, LIDAR scanning, and ocean-floor mapping provide centimeter-scale precision for tracking tectonic motion, sea level rise, and volcanic deformation in near real time.
Frequently Asked Questions
Formula
n = Vv/Vt = 1 - (bulk density / grain density)
Porosity n equals the void volume divided by total volume, or equivalently 1 minus the ratio of bulk density to grain density. Void ratio e = n/(1-n). Permeability is estimated using the Hazen formula K = C * d10^2 for clean sands, or the Kozeny-Carman equation which relates permeability to porosity cubed divided by (1-n) squared times grain diameter squared divided by 180.
Frequently Asked Questions
What is the difference between porosity and permeability?
Porosity is the fraction of void space in a material relative to its total volume, expressed as a percentage. It describes how much fluid a material can hold. Permeability, on the other hand, measures how easily fluids can flow through the connected pore spaces. A material can have high porosity but low permeability if the pores are not well connected, like clay which has 40 to 60 percent porosity but very low permeability. Conversely, fractured rock may have low porosity but high permeability along the fractures.
How is porosity measured in the laboratory?
There are several methods to measure porosity. The direct method involves saturating a dry sample with water and measuring the volume of water absorbed. The density method calculates porosity from the grain density and bulk density of the sample using the formula n = 1 minus bulk density divided by grain density. Gas pycnometry uses helium gas to measure the true volume of solid grains. For rocks, mercury injection porosimetry forces mercury into pores at increasing pressures to map the pore size distribution and total porosity.
What factors affect the porosity of soil and rock?
Grain size distribution is one of the biggest factors, where well-sorted (uniform) soils have higher porosity than poorly sorted soils because small grains fill the voids between larger ones. Grain shape matters too, as angular grains pack less efficiently than rounded ones, creating more void space. Compaction and cementation reduce porosity over time. Depth of burial increases overburden pressure which compresses pores. Biological activity and root growth can create secondary porosity, while mineral precipitation can reduce it.
How do porosity and permeability relate to groundwater availability?
A good aquifer needs both high porosity and high permeability. Porosity determines the total volume of water that can be stored, while permeability controls how fast that water can be extracted. Specific yield, which is the fraction of water that drains by gravity, is typically 60 to 80 percent of total porosity for sand and gravel aquifers. Clean sand and gravel make excellent aquifers because they have moderate porosity (25 to 40 percent) combined with high permeability, allowing wells to produce large volumes of water sustainably.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.
Does Porosity and Permeability Calculator work offline?
Once the page is loaded, the calculation logic runs entirely in your browser. If you have already opened the page, most calculators will continue to work even if your internet connection is lost, since no server requests are needed for computation.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy