How many ticks must I use to get only one item through a hopper?

Solution 1:

Pistons also have a .5 tick on the end. the game gives off-tick checks to increase speed, to there are 2 game-ticks in every redstone tick. Therefor 8 game-ticks, or 4 redstone ticks.

Solution 2:

An item will pass through a hopper every .4 seconds. A Minecraft tick is 1/20th of a second, or 0.05s.

So, that means every 0.4s 8 ticks occur. Therefore, you will need to wait 8 ticks in order to get 1 item through a hopper.

This holds true for Bukkit servers as well.

Solution 3:

It really depends on the configuration of the server. I recommend using comparator to check if the item got inside of the hopper and lock it.