Over jumps and galloping, no more than 200 lbs For everything else, a horse should carry no more than 20% of their body weight on their backs. For the largest horse, this is about 250 lbs. Draft horses were not bred for riding, so their backs are a bit weaker and should only carry 15% of their weight, which works out to 300 lbs for the very largest draft horse. These weights all include the weight of tack.