The Standard Penetration Test (SPT) is a widely used in-situ test to evaluate soil properties. It measures penetration resistance by counting the number of blows (N-value) needed to drive a split spoon sampler 300 mm into the ground using a 65 kg hammer falling from 750 mm. The N-value indicates the degree of compactness for cohesionless soils (e.g., sand) and consistency for cohesive soils (e.g., clay), aiding in foundation design and assessing liquefaction potential under dynamic forces like earthquakes. Measures undisturbed soil strength and liquefaction resistance. A 65 kg weight drops 750 mm to drive a sampler 300 mm; blow count (N) is recorded. Foundation design, soil classification, and seismic risk assessment.