Porosity converter
Convert porosity between the percentage geologists use and the void ratio soil engineers use.
That's 1.14× as open as loose sand, while soft clay is 1.25× higher. A cubic meter of it could hold about 400 liters of water.
What it means
How much space is in it?
Densities assume a grain density of 2.65 g/cm³, which suits quartz sands and most soils but not iron ores or organic soils.
Every unit
Your porosity in every unit
Learn
Three things worth knowing
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e = n ÷ (1 − n)
With n as a fraction. A porosity of 40% is a void ratio of 0.67; a void ratio of 1 is a porosity of 50%.
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Why engineers use the void ratio
Compacting soil squeezes out voids but never the grains. Keeping the solid volume in the denominator means settlement calculations have one variable instead of two.
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Porosity is not permeability
Clay can be 50% pore space and nearly waterproof, because the pores are tiny and poorly connected. Space is not the same as a path.
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Popular porosity conversions
Background
About porosity and void ratio
Porosity is voids divided by the whole volume; void ratio is voids divided by the solids. A porosity of 50% is a void ratio of 1.0, because half and half means one to one.
Soil mechanics prefers the void ratio because the solid volume does not change when soil is compressed, so only one number in the fraction moves.