Weight alone is not the only determining factor when choosing a horse that suits you.
The size of your horse should be proportional to you and height as well as riding skills all need to be considered. The goal is to make the horse’s job as easy as possible and the rider feel secure and comfortable in the saddle.
So, in some cases, a heavier or taller rider can sit a smaller horse and sometimes a small but skilled rider can confidently ride a bigger horse.
Your riding skill
One of the most important things, besides your size, that will determine what kind of horse is good for you, is your riding skill.
The fastest way to get better at riding is to take regular lessons. A rider who is a skilled equestrian – balanced in the saddle and has a good seat – will be easier for any horse to carry than a rider who is sloppy and unbalanced on horseback.
A horse that has to carry an unbalanced rider will quickly develop problems with his back, soundness and even behaviour.
When you are supple, balanced and know how to carry yourself in the saddle, your horse will be more comfortable and surefooted as well as stay sound for longer.
How much weight can a horse carry?
The Journal of Veterinary Behaviour published a study that suggests a rider should weigh no more than 15% of the horse’s body weight.
Though there is some debate about this number, a generally accepted rule of thumb is that a horse can carry between 15 to 20 per cent of his own body weight.
In addition to the rider, tack and other equipment are included in that total weight.
If a horse is out of shape, overweight or underweight, his capacity to carry will be diminished and he may not even be able to carry 10 or 5 per cent of his body weight.
You need to adjust the load to the horse’s capabilities and fitness level. An out of shape horse needs to have his fitness built up, with proper diet and exercise, gradually so that he may be able to carry tack and rider.
Choosing the right tack
Make sure that you’re using the right type and size tack with your horse. The saddle needs to fit your horse and will often require several fittings over a period of time, after which regular adjustments need to be made.
The saddle is critical in distributing your weight correctly over the horse’s back and keeping you balanced. The proper saddle, adjusted correctly, will ensure that your horse does not end up with a sore back.
With tack that is right for your horse and agreeable to you (that it fits your horse is more important) you will both be more comfortable, be able to communicate better and be less stressed during rides.

The rider’s height
In addition to your own physical condition and personal command of your body, your height impacts your surety in the saddle.
If you’re tall, a shorter, finely boned horse can make you feel top-heavy. A sturdy type such as a Fjord or an Icelandic horse may be more comfortable for you than a Thoroughbred or Arabian.
A horse that makes you feel unbalanced due to its build is not a suitable horse for you. If you’re feeling unbalanced, you will transmit that to the horse which will, in turn, become less secure and more prone to accidents.
When you’re choosing a horse for yourself, make it a point to try many different sizes and builds of horses. You may find that you dislike very tall horses, but that a shorter but wide-barrelled horse may be comfortable for you.
If your body type is stockier, consider horses such as the Quarter Horse, drafts or draft crosses.
If your build is more slender, breeds such as Thoroughbreds, Friesians or warmbloods may better suit you.
Carefully consider the type of horse you want and see and ride as many possibilities as you can before making the decision to buy.
Taking into consideration the horse’s age
When a horse is young, his bones and joints are still developing. As he ages and becomes a senior, he will begin encountering stiffness and even arthritis in his joints.
Very young and very old horses need to carry less weight.
The overall workload of a young horse, still physically in the process of maturing, and an old horse, that may or may not have joint issues, needs to be lighter than that of a horse in his prime.
This includes the weight of the rider and tack as well as the length and intensity of the workload.
Just as with people, children and the elderly, cannot physically perform as a fit adult can and there is no reason to treat horses any differently.