Arrow Interception Sizes

General Interception Rules
You may intercept any projectile less than 10 times the weight of your own ammunition. Attempts to intercept heavier projectiles fail. You may also intercept magical effects, so long as they are visible and require or sometimes require an attack roll. For example, eldritch blast always requires a roll, and fireball sometimes does, so they can be blocked, but chain lightening does not, and cannot be. For magical effects, you take a -5 penalty to your attack roll. If you succeed, the spell effects the arrow instead of the intended target. Usually this just destroys the arrow, but some spells have other effects (for example, fireball detonates with normal strength centered on the arrow). You choose where along the spell's path the interception occurs (within one range increment of you).

Weight of projectiles in pounds for creatures of various sizes: