Almost every ammunition manufacturer has a table that shows how much almost any given round will drop.
This, for instance, is from Remington:
Remington's Ballistic Chart For Remington.223 AmmunitionFigure out where YOUR zero is and adjust your scope from there.
For instance this from that Remington page:
Premier® AccuTip™ 55 * * 1.5 * * 1.4 * * zero * * -2.8 * * -7.1 * * -21.7 * * -46.3
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Zeroed at 200 yards, 1.5 High at 100 yards, 1.4 inches high at 150, zero at 200, 2.8 inches lower at 250 yards, 7.1 inches lower at 300 yards, 21.7 inches lower at 400 yards and 46.3 inches lower at 500 yards.
Some other companies go out further.
Just remember that ¼ inch click at 100 is ½ inch click at 200 yards, 3/4 of an inch at 300, a full inch at 400 and 1¼ inches at 500.
I often shoot at 600 yards.
That means that I have a 1½ inch adjustment for each of the dials.
Of course you can always try to find a BDC, or Bullet Drop Compensator. Some Scope manufacturers have them as an extra option.