Pore Water Pressure Calculator

Why pore pressure matters for foundation design

Water filling soil pore spaces below the water table exerts hydrostatic pressure just like water in a tank, and this pressure directly reduces the effective stress that controls soil strength - making accurate pore pressure estimates essential for safe foundation and slope design.

Worked example

For a point 10 meters below the water table, in water with a density of 1,000 kg/m³:

u = (1000 x 9.807 x 10) / 1000 = 98.07 kPa

Frequently asked questions

Does this account for flowing groundwater? No - this is the hydrostatic (static) pore pressure assuming no vertical groundwater flow. Under active seepage conditions, actual pore pressure can differ from this simple hydrostatic estimate and requires flow-net or numerical seepage analysis instead.

How is this used afterward? This pore pressure value plugs directly into Terzaghi's effective stress equation (Effective Stress = Total Stress - Pore Pressure), which is the next step in most geotechnical bearing capacity and slope stability calculations.