Effective Stress Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026The foundation of modern soil mechanics
Karl Terzaghi's effective stress principle explains a critical insight: not all the stress applied to saturated soil is carried by the soil particles themselves. Part of it is carried by the water filling the pore spaces, and only the remainder, the effective stress, is transmitted through grain-to-grain contact.
Worked example
For a soil layer under 200 kPa of total stress with 80 kPa of pore water pressure:
Effective Stress = 200 - 80 = 120 kPa
Effective stress, not total stress, controls soil strength and compressibility - this is why a sudden rise in pore water pressure (from an earthquake, heavy rainfall, or rapid loading) can trigger soil liquefaction: effective stress drops toward zero, and the soil momentarily loses its ability to resist shear like a solid.