A good rule of thumb is that every 20 grains of point weight equals 3 to 4 pounds of spine. By that, I mean that if an arrow is properly spined at 64 pounds with a 100 grain tip, if you change to a 125 tip the bow will need to be turned down to around 60 pounds for the arrow to regain the same stiffness. That's a pretty significant change in spine.

On the other hand, it's interesting to note that a point weight change of 25 grains means VERY LITTLE in terms of the overall weight of the arrow. For a 400 grain total arrow weight, 20 grains represents only about 5% of the total, which dictates Kinetic Energy. What does this mean? Point weight adjustments are mainly intended to help achieve proper arrow spine, NOT to increase the "hitting power" or penetration of the arrow.