Use your hydrometer and measure the SG. Compare that with your expected FG (should be specified in the recipe). If it's in range of the FG, take another reading a couple days latest to verify no more activity.
The hydrometer is the only way to know for sure that your fermentation is done.
Arguing on the internet is like running in the Special Olympics, even if you win you're still retarded.
My internet friends were making fun of my kegdolly and I took it out on Gary. - Ginger