According to mlb.com, baseball bat's cannot exceed 42 inches, or 106.68 cm (1 inch = 2.54 cm). From Wikipedia, the average mass of a baseball bat is 0.96 kg. You can check the mass by weighing an average baseball bat, then dividing that number by 9.8 m/s^2. If you need any more help, don't hesitate to ask! According to mlb.com, baseball bat's cannot exceed 42 inches, or 106.68 cm (1 inch = 2.54 cm). From Wikipedia, the average mass of a baseball bat is 0.96 kg.