How heavy and how long does an external hemorrhoid bleed for?

Few days: You are referring to ext. Hems. Which thrombose (clot) from blood slowing down as it traverses the hem. Vein it is going thru as you strain to have a bm or go too often with loose stools. Once the blood clots in the vein it swells and hurts and sometimes it bursts open and bleeds on its own or the doctor opens it to get the clot out and reduce the swelling and pain lasting a few days.

Mild: External hemorrhoids generally do not bleed in great quantity or for too long. They can bleed if thrombosed or clotted, and they can rupture, causing some bleeding for a few days. Internal hemorrhoids are more often responsible for significant bleeding.