Conclusions: The standard compressive strength of the first class brick is about 10.3 N/mm2, or 10,300 kN/m2, or 105 kg/cm2, or 1,493 PSI and 2nd class brick is 70 kg/cm2. The compressive strength of bricks can vary, but generally, 1st class bricks have a compressive strength of around 10 N/mm² or 100 kg/cm², while 2nd class bricks have a ...Web