Relationships between strength and Rockwell F as well as Meyer hardness numbers of Al-7wt.%Si alloys with three different levels of Mg were determined. An excellent correlation was found between hardness and tensile strength. The relationship between hardness and yield stress depended on the temper of the alloy. The relationship between Rockwell hardness and both tensile strength and yield stress follows a curve. Tensile strength acid yield stress change linearly with Meyer hardness.