Hydraulic Conductivity Converter (cm/s, m/day)

Typical values

Clean gravel 1–100 cm/s, coarse sand 10⁻²–1 cm/s, fine sand 10⁻⁴–10⁻² cm/s, silt 10⁻⁶–10⁻⁴ cm/s and clay below 10⁻⁷ cm/s. Landfill clay liners are specified at k ≤ 10⁻⁷ cm/s (10⁻⁹ m/s).

Hydraulic conductivity or permeability?

Hydraulic conductivity K depends on both the soil and the fluid (water at a stated temperature). Intrinsic permeability k = Kμ/(ρg) depends only on the pores and is measured in m² or darcies: for water at 20 °C, 1 darcy ≈ 9.6 × 10⁻⁴ cm/s.

Hydraulic Conductivity unit definitions

metre per second (m/s)

Hydraulic conductivity K in metres per second is the SI unit of Darcy’s law, q = K i: the flow per unit area under a hydraulic gradient of one. Clean gravel is about 10⁻² m/s, sand 10⁻⁵–10⁻³ m/s and clay below 10⁻⁹ m/s.

centimetre per second (cm/s)

Centimetres per second are the unit most soil-mechanics texts and GATE questions use for the coefficient of permeability k: about 1 cm/s for gravel, 10⁻³ cm/s for fine sand and 10⁻⁷ cm/s for clay.

metre per day (m/day)

Metres per day are the usual unit of hydraulic conductivity in groundwater hydrology and well design, because aquifer flows are slow: a sandy aquifer is about 10–50 m/day.

centimetre per hour (cm/h)

Centimetres per hour express infiltration rates and the saturated conductivity of agricultural soils: about 2.5 cm/h for a sandy loam and under 0.1 cm/h for clay.

millimetre per hour (mm/h)

Millimetres per hour measure infiltration and sprinkler application rates; a sprinkler must apply water slower than the soil’s basic infiltration rate, often 5–25 mm/h.

foot per day (ft/day)

Feet per day are the US unit of hydraulic conductivity in USGS reports and groundwater models such as MODFLOW run in US units.

Popular hydraulic conductivity conversions

• metre per second to centimetre per second
• centimetre per second to metre per second
• centimetre per second to metre per day
• metre per day to centimetre per second
• millimetre per hour to centimetre per hour
• foot per day to metre per day

Related converters

• Permeability Converter (Darcy, Millidarcy, m²) – darcy, mD, m², µm²
• Discharge Converter (Cumecs, Cusecs, MLD) – cumecs, cusecs, MLD, MGD, L/s
• Speed Converter – km/h, mph, m/s, ft/s, knots
• Printable hydraulic conductivity conversion chart – print, PDF or PNG
• Darcy’s law calculator
• intrinsic permeability converter (darcy, m²)
• Permeability Test Calculator – Constant-head or falling-head test readings → coefficient of permeability.
• Sprinkler Irrigation Calculator – Discharge and spacing → application rate; catch-can depths → CU and DU.
• Drain Spacing Calculator – K, water-table height, equivalent depth and drainage coefficient → drain spacing.
• Infiltration Calculator – Model parameters and time → infiltration rate and cumulative depth.

Sources

• The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures.
• Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 Edition, National Institute of Standards and Technology.

Last reviewed: 2026-10-15.