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Hydraulic Conductivity and Permeameter Calculator

Calculate laboratory saturated hydraulic conductivity with either a constant-head or conventional falling-head permeameter relationship. For constant-head testing, K equals collected volume V times specimen length L, divided by specimen area A, total-head difference delta h, and elapsed time delta t. The specimen area is calculated from its entered cylindrical diameter. The calculator also reports measured discharge, Darcy flux, and hydraulic gradient so the arithmetic can be independently checked. For falling-head testing, K equals standpipe area a times specimen length L divided by specimen area A and elapsed time delta t, multiplied by the natural logarithm of initial head h1 divided by final head h2. The initial head must exceed the final positive head for this stated arrangement. Geometry and head inputs share one selected unit: millimetres, centimetres, metres, or inches. Constant-head volume supports millilitres, litres, cubic centimetres, and cubic inches. Time supports seconds, minutes, and hours. All values are normalized internally to SI units. Results are displayed in metres per second, centimetres per second, metres per day, and feet per day. These equations assume saturated, one-dimensional Darcy flow through the measured specimen area. Heads must use one datum and describe the actual total-head difference across the specimen. Flow that bypasses through a sidewall gap, fitting, tubing leak, crack caused by preparation, or other preferential path is not valid specimen flow. Stabilized readings, apparatus calibration, saturation procedures, backpressure where required, repeated intervals, replicate specimens, and complete raw observations remain governed by the applicable laboratory method. Hydraulic conductivity depends on both the porous medium and the test fluid. Water temperature, viscosity, density, chemistry, entrained air, effective stress, fabric, disturbance, saturation, gradient, and boundary conditions can change a measured value. Intrinsic permeability is a different area-dimension property of the medium. This calculator does not silently convert K to intrinsic permeability or correct results to another temperature or fluid because those steps require documented compatible density and viscosity data. Very high gradients, non-Darcy flow, consolidation, chemical alteration, changing saturation, apparatus resistance, membrane effects, an

Verification resources

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

  • undefined. Documents constant-head and falling-head laboratory methods, apparatus, calculations, applicability, and reporting considerations.
  • undefined. Shows the falling-head specimen and standpipe measurements, logarithmic head term, elapsed time, and permeability calculation workflow.
  • undefined. Provides federal laboratory testing context and reporting workflows for constant-head and falling-head permeability tests.
  • undefined. Distinguishes saturated hydraulic conductivity from intrinsic permeability and relates both to porous-medium and fluid properties.

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Common questions

What is the constant-head permeability equation?
For steady saturated flow through a cylindrical specimen, K = V L divided by A delta-h delta-t, where V is collected volume, L is specimen length, A is specimen area, delta-h is total-head difference, and delta-t is elapsed time.
What is the falling-head permeability equation?
For the stated conventional arrangement, K = a L divided by A delta-t, multiplied by the natural logarithm of h1 divided by h2. The initial head h1 must exceed the final positive head h2.
Is hydraulic conductivity the same as intrinsic permeability?
No. Hydraulic conductivity reflects both the porous medium and fluid properties. Intrinsic permeability describes the medium and has dimensions of area. Converting between them requires compatible density, viscosity, and gravity values.
Does this replace a laboratory standard or report?
No. Use the governing method, calibrated apparatus, required saturation and backpressure procedures, temperature or viscosity treatment, quality controls, and reporting rules for the actual test.

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