It is important to know how much your bullet drops over the distance you are shooting. However, there is no rule for that. It depends what calibre bullet and what grain you're using. The following graphs pertain to the two most popular calibres - the 270 Win and the 30-06 Springfield. The basis applied is that the guns are zeroed on 200 metres.
It is clear that the bullet drops considerably after 250 metres - to almost ruler length - a mere 50 metres further than the gun was zeroed at. If the gun had been zeroed at 100 metres, the effect would be even more drastic. Therefore, ensure that the gun has been zeroed at 200 metres and determine how far the bullet drops after that. This distance should be ingrained in your mind, because on the hunting ground that decision has to be taken within a second.