Permeability Test Calculator
A constant-head test that collects 500 cm³ in 600 s through a 15 cm long, 78.54 cm² sample under a 40 cm head gives k = 0.00397886 cm/s, typical of a medium sand.
A 100 mm diameter mould has A = 78.54 cm².
0.00397886427298192 cm/s
Full answer, then cut to fewer decimals (not rounded):
- 0.00397886427298192 cm/s
- 0.0039788642729819 cm/s
- 0.003978864272981 cm/s
- 0.00397886427298 cm/s
- 0.0039788642729 cm/s
- 0.003978864272 cm/s
- 0.00397886427 cm/s
- 0.0039788642 cm/s
- 0.003978864 cm/s
- 0.00397886 cm/s
- 0.0039788 cm/s
- 0.003978 cm/s
- 0.00397 cm/s
- 0.0039 cm/s
- 0.003 cm/s
- In m/s
- 0.00003978864273 m/s
- In m/day
- 3.437738732 m/day
- Typical soil
- sand (medium)
Step-by-step solution
- k = QL / (A h t) = 500 × 15 ÷ (78.54 × 40 × 600)
- k = 0.003978864273 cm/s
Permeability Test Formula
k = QL/(Aht); k = 2.303 (aL/At) log₁₀(h₁/h₂)
a standpipe area, A sample area, L sample length, h head, t time
Worked Example
A constant-head test collecting 500 cm³ in 10 minutes through a 15 cm sample of 78.54 cm² under 40 cm head:
- k = QL / (A h t) = 500 × 15 ÷ (78.54 × 40 × 600)
- k = 0.003978864273 cm/s
In m/day: 3.437738732 m/day · Typical soil: sand (medium)
GATE tip
Keep every length in cm and time in s; then k comes out in cm/s, the unit GATE answer keys usually use.
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Frequently asked questions
When is the falling-head test used?
For fine soils (silts and clays) where too little water passes for a constant-head test to measure accurately.
Why does the falling-head formula have 2.303?
Integrating −a dh/dt = kAh/L gives a natural log; 2.303 converts ln to log₁₀.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
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APA
Scientific Converters. (2026, October 15). Permeability Test Calculator. Retrieved October 29, 2026, from https://scientificconverters.com/calculators/permeability-test-calculator/
IEEE
Scientific Converters, "Permeability Test Calculator," scientificconverters.com. Accessed: Oct. 29, 2026. [Online]. Available: https://scientificconverters.com/calculators/permeability-test-calculator/