ToolsGeotechnicalPermeability & Soakaway

Permeability Correlation Estimator

Estimate hydraulic conductivity from grain size using Hazen, Breyer, and Kozeny-Carman correlations. Enter D10 from sieve analysis to get K in m/s.

Last updated 15 September 2026

About this tool

Estimate hydraulic conductivity from grain size distribution data using three published empirical correlations: Hazen (1892), Breyer (1964), and Kozeny-Carman.

All three methods use D10 (the 10% passing size from a sieve analysis). Hazen needs only D10. Breyer is valid for a specific D10 range. Kozeny-Carman also uses porosity or void ratio for a more refined estimate.

Useful for preliminary permeability estimates when field test data is unavailable. Use the Sieve Analysis Calculator to determine D10 from your grading data. Always compare against field test results for design.

How to use this tool

1. Enter D10 — the 10% passing size in mm from a particle size distribution test.

2. Optionally enter porosity or void ratio — required for the Kozeny-Carman correlation.

3. Compare the three estimates — use the spread to inform engineering judgement.

Technical information

Hazen: K = C × D10² (C = 100, D10 in cm, K in cm/s)

Breyer: K = (g/ν) × 6×10⁻⁴ × D10² (D10 in m, valid 0.06–0.6 mm)

Kozeny-Carman: K = (g/ν) × (n³/(1-n)²) × D10² / 180 (D10 in m)

g/ν at 20°C = 9.77 × 10⁶ m⁻¹s⁻¹. All results converted to m/s.

Limitations

All correlations assume clean, uniformly graded granular soils with no fines. They are not valid for clay, silt-dominated soils, organic soils, or gap-graded materials.

Hazen's C = 100 is the most commonly cited value but can range from 40 to 150 depending on grain shape and sorting. The estimate can easily be off by a factor of 2–3.

These are preliminary estimates only. For design, always verify against field permeability tests (constant head, falling head, or pumping tests).

Revision history

15 September 2026: Initial release

Disclaimer

This tool is provided for educational and general information purposes only. It is not a substitute for professional engineering advice, design or verification.

Diggy and its contributors are not licensed engineering consultants and no results generated by this tool should be used directly for construction, design or safety-critical decisions.

All values and outputs are based on published empirical correlations and should be independently checked and confirmed by a qualified geotechnical engineer before use.

By using this tool, you accept full responsibility for how you interpret and apply the information provided.

Spotted an error? Let us know.

D10 — effective grain size (mm)

10% passing size from particle size distribution. Use the Sieve Analysis Calculator if needed.

Optional — for Kozeny-Carman

Porosity (n)

Or void ratio (e)

Enter either porosity or void ratio — the other is calculated automatically.

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