Check out my uphill chart,I would have to shoot a 70 yard shot on 45 deg angle for 51.4 yards and if it were the same shot downhill,I would have to shoot it for 47.8.
THIS IS FOR MY SETUP but most will be very similar.

The horizontal distance is the most important.As you can see,sight paralax(as will gravity to some degree)changes the shot at extreme distances on uphill/downhill shots but for most in normal hunting stuations,the horizontal number is all you need.


Remember that gravity doesn't know the hill is there so it is pulling the arrow to the center of the earth as KA refers to.