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Porosity and Void Ratio Calculator

Porosity and void ratio describe pore space with different denominators. Total porosity, n, is void volume divided by total bulk volume. Void ratio, e, is void volume divided by solid volume. Their exact conversions are n = e divided by 1 + e and e = n divided by 1  n . GeoMiner accepts five transparent input workflows. For a dry specimen, total porosity is n = 1  dry bulk density divided by particle or grain density. For a fluid-filled bulk-density measurement, n = matrix density  measured bulk density divided by matrix density  pore-fluid density . For measured volumes, n = void volume divided by total volume. The calculator also converts a known porosity percentage to void ratio and a known void ratio to porosity. Densities within one calculation must use the same unit, and volumes must use the same unit; the ratios are dimensionless. Dry bulk density cannot exceed the matching particle density, measured fluid-filled bulk density must lie above pore-fluid density and at or below matrix density, void volume must be smaller than total volume, and porosity must remain below 100 percent. A mathematically valid result is not automatically representative. Particle or matrix density varies with mineralogy, organic matter, alteration, cement, mixed grains, and assumptions. Bulk density varies with sample preparation, moisture, saturation, fractures, weathering, scale, and whether the measurement represents a plug, hand sample, soil clod, sediment sample, core interval, or borehole-log response. Total porosity includes pore space represented by the measurement, including pores that may be isolated. Effective porosity represents connected pore space relevant to flow. This calculator does not infer effective porosity, pore-throat geometry, permeability, hydraulic conductivity, specific yield, storage, saturation, strength, consolidation, compaction, or flow behaviour. Two materials with the same total porosity can have radically different transport and engineering behaviour. Use measured, representative inputs and preserve the method, condition, scale, units, uncertainty, and assumptions. Laboratory testing, calibrated log interpretation, groundwater evaluation, petroleum work, compaction acceptance, geotechnical design, resource work, and other consequential uses require applicable procedures and qualified interpretation. Exact densities, volumes, porosity, and

Verification resources

Cross-check terminology, classification, methods, and safety with these authoritative external resources.

  • undefined. Defines total porosity and derives porosity as one minus dry bulk density divided by particle density, while explaining why bulk density depends on sample condition.
  • undefined. Calculates rock porosity from grain density and dry bulk density and documents material heterogeneity within core samples.
  • undefined. Provides the fluid-corrected density-log porosity relationship and explains the importance of matrix and pore-fluid density assumptions.
  • undefined. Defines porosity and void ratio as distinct dimensionless volume relationships and provides soil phase-relation context.

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Common questions

What is the difference between porosity and void ratio?
Porosity is void volume divided by total volume. Void ratio is void volume divided by solid volume. Both are dimensionless, but they use different denominators. The exact conversions are n = e/(1+e) and e = n/(1n).
How do I calculate porosity from density?
For a dry sample, total porosity is one minus dry bulk density divided by particle or grain density. Use densities in the same unit. For a fluid-filled density measurement, matrix and pore-fluid density must also be represented.
Is total porosity the same as effective porosity?
No. Total porosity includes all pore space represented by the measurement, including pores that may be isolated. Effective porosity is the connected pore space that contributes to flow. This calculator does not infer connectivity or permeability.
Can I use an assumed particle density?
An assumption can support a clearly labelled classroom example or first-pass check, but mineralogy, organic matter, alteration, cement, and mixed grains can change particle density. Use a representative measurement when the result matters.
Can this calculator replace laboratory testing or log interpretation?
No. Sample preparation, moisture and saturation state, scale, heterogeneity, closed pores, mineralogy, borehole conditions, calibration, and corrections all affect defensible porosity. Use fit-for-purpose methods and qualified interpretation for consequential work.

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