Depending on the muzzle velocity, your drop at 100 when sighted for 50 will be somewhere around 4 inches. (assuming full power load approx. 1200fps+)
Faster drops slightly less, slower will drop more.
To know about how much, you need the bullet weight and muzzle velocity. To know exactly how much, you also need the ballistic coefficient of the bullet to plug into the formula.
For example (without using the real numbers), a bullet with a more blunt nose shape might have a drop of 4.1" where one (of equal weight and speed) with a more pointed nose profile might have a drop of 3.8".
hope this helps.