If you do not know your horse’s seat size you will need to try a few for size. Afterall, the saddle needs to fit you as well as the horse. A seat too small will affect the rider’s position in the saddle, likewise a seat too big can often cause the rider to ‘ride behind their horse’ plus many more issues.
Measuring a seat for the rider - a general indicator is to sit on a chair and position your thigh at a right angle to your lower leg. In this position, measure from your buttocks to the knee in a straight line – this measurement should give you your upper leg length which can then be converted to an approximate seat size. Of course it is important to note that your seat size may not always be suitable for your horse and your horse’s needs also need to be assessed before making any decisions.
Measurement Approx. seat size
Up to 41cm 15” Seat
Up to 46cm 16" Seat
Up to 50cm 16½” Seat
Up to 54cm 17" Seat
Up to 58cm 17½" Seat
59cm or longer 18" Seat
(Source: adapted from Thorowgood)
When fitting a seat for the horse, the saddle should not pass over last rib. If your saddle seat falls over this threshold it may put unnecessary pressure on internal organs such as the kidneys. A correct fitting seat should ideally fall before the last rib to avoid any unwanted pressure. Again, as mentioned previously, it is always a good idea to have a professional look over your saddle to ensure the fit is right for both horse and rider collectively.