How much blood will i lose during foot amputation?

Not much: It should not be enough to require a transfusion unless you are anemic beforehand. Your surgeon will use a tourniquet during surgery if he is concerned about blood loss. Many times an amputation is required because there isn't enough blood to a limb, in which case blood loss should be minor.

Depends : It all depends on the level of the amputation and what the surgeon decides to do with the main arteries of your feet. I usually hand tie the arteries to prevent a lot of bleeding. But the arteries could be too small. Major foot amp, trans met amp, which half of the foot is amputated, is the amputation with highest bleeding rate. I would estimate 50-75ml of actual blood loss.

It depends.: It depends on the quality of your circulation and on the procedure performed.