What do horse's weigh?

A horse should never carry any more than 20% of it's own body weight, this includes the tack and rider.
A horse should only carry 20% of it's own weight, so if a horse weighs 1,200 pounds, the rider would at the most be 100 pounds. The reason why I said 100 pounds instead of 120 pounds is because of the tack (mainly the saddle).