Which equivalent in LED do I have to choose to replace my 50Watt halogen spot?

A few simple rules to choose the equivalent in LED:

1. Replacement of classic incandescent lamps: I choose for a LED lamp that has 10 times less power
2. Replacement of halogen lamps: I choose a LED lamp that has 8 times less power
3. Energy saving bulb or classic fluorescent tubes: I choose a LED lamp that has 2.5-3 times less power.